Merge pull request #1 from rbock/master

Update repo for rbock

.travis.yml

@@ -0,0 +1,32 @@
+language: cpp
+
+os:
+  - linux
+
+compiler:
+  # - clang # disabled clang due to missing libc++
+  - gcc
+
+notifications:
+ email:
+   on_success: change
+   on_failure: always
+
+before_install:
+  - sudo add-apt-repository ppa:ubuntu-toolchain-r/test -y
+  - sudo apt-get update
+  - if [ "$CXX" = "g++" ]; then sudo apt-get install g++-4.8; fi
+  - if [ "$CXX" = "g++" ]; then export CXX="g++-4.8" CC="gcc-4.8"; fi
+
+
+install:
+  - "mkdir -p $TRAVIS_BUILD_DIR/build/scripts"
+  - "cd $TRAVIS_BUILD_DIR/build/scripts"
+  - "cmake $TRAVIS_BUILD_DIR"
+
+script:
+  - "cd $TRAVIS_BUILD_DIR/build/scripts"
+  - "make -j3"
+  # test compile-time constraints
+  - "make test_sqlpp_constraints"
+

CMakeLists.txt

@@ -23,6 +23,10 @@
 # SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 cmake_minimum_required(VERSION 2.6)
+
+# Cygwin does not define WIN32 and warn if not use with this flag
+set(CMAKE_LEGACY_CYGWIN_WIN32 0) # Remove when CMake >= 2.8.4 is required
+
 project (sqlpp11)
 enable_testing()
 
@@ -34,10 +38,11 @@ elseif ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU")
 endif ()
 
 set(include_dir "${PROJECT_SOURCE_DIR}/include")
-file(GLOB_RECURSE sqlpp_headers ${include_dir}/*.h)
-include_directories(${include_dir})
+file(GLOB_RECURSE sqlpp_headers "${include_dir}/*.h")
+include_directories("${include_dir}")
 add_subdirectory(tests)
 add_subdirectory(test_constraints)
+add_subdirectory(examples)
 
 install(DIRECTORY "${PROJECT_SOURCE_DIR}/include/sqlpp11" DESTINATION include)
 

CREDITS

@@ -7,8 +7,12 @@ This library evolved through several stages and would probably not exist without
 	* Peter Knoblach: Initial ideas
 	* Ulrich Küttler: Feedback and extensions
 
+
 	* Metafeed GmbH: Production code using a forerunner version
 	* PPRO Financial Ltd: Production code using sqlpp11 and a forerunner version
+	* The boost community: Invaluable suggestions and critiques
+
+  * Meeting C++ Munich: Hosted the first talk about sqlpp11
 
 
 If you miss your name of this list, please let me know.

README.md

@@ -5,9 +5,11 @@ A type safe embedded domain specific language for SQL queries and results in C++
 
 Extensive documentation is found in the wiki, https://github.com/rbock/sqlpp11/wiki
 
-Upcoming talks at 
+Upcoming talks/workshops) at 
   * CppCon (Bellevue, Washington, USA): http://cppcon.org
-   * 2014-09-11: http://sched.co/1r4lue3
+   * 2014-09-08: http://sched.co/1qhngYK (Workshop Part 1)
+   * 2014-09-11: http://sched.co/1r4lue3 (Talk)
+   * 2014-09-12: http://sched.co/Wi8aWM (Workshop Part 2)
   * MeetingC++ (Berlin, Germany): http://meetingcpp.com/index.php/mcpp2014.html
    * 2014-12-05:http://meetingcpp.com/index.php/tv14/items/4.html
    
@@ -105,6 +107,7 @@ sqlpp11 makes heavy use of C++11 and requires a recent compiler and STL. The fol
   * clang-3.2 on Ubuntu-12.4
   * clang-3.4 on Ubuntu-12.4
   * g++-4.8 on Ubuntu-12.4
+  * g++-4.8 on cygwin 64bit
   * g++-4.9 on Debian Unstable
 
 __Database Connector:__

examples/CMakeLists.txt

@@ -0,0 +1,22 @@
+
+macro (build arg)
+	# Add headers to sources to enable file browsing in IDEs
+	include_directories("${CMAKE_SOURCE_DIR}/tests")
+	add_executable("Sqlpp11Example${arg}" "${arg}.cpp" ${sqlpp_headers} "${CMAKE_SOURCE_DIR}/tests/MockDb.h" "${CMAKE_CURRENT_LIST_DIR}/Sample.h")
+	add_test("${arg}" "${arg}")
+endmacro ()
+
+#build(sample)
+build(insert)
+build(update)
+build(remove)
+build(select)
+
+#find_package(PythonInterp REQUIRED)
+
+#add_custom_command(
+#	OUTPUT ${CMAKE_CURRENT_LIST_DIR}/Sample.h 
+#	COMMAND ${PYTHON_EXECUTABLE} ${CMAKE_SOURCE_DIR}/scripts/ddl2cpp ${CMAKE_CURRENT_LIST_DIR}/sample.sql Sample test
+#	DEPENDS ${CMAKE_CURRENT_LIST_DIR}/sample.sql
+#	)
+

examples/Sample.h

@@ -0,0 +1,142 @@
+#ifndef TEST_SAMPLE_H
+#define TEST_SAMPLE_H
+
+#include <sqlpp11/table.h>
+#include <sqlpp11/column_types.h>
+
+namespace test
+{
+  namespace TabPerson_
+  {
+    struct Id
+    {
+      struct _name_t
+      {
+        static constexpr const char* _get_name() { return "id"; }
+        template<typename T>
+        struct _member_t
+          {
+            T id;
+            T& operator()() { return id; }
+            const T& operator()() const { return id; }
+          };
+      };
+      using _traits = sqlpp::make_traits<sqlpp::integer, sqlpp::tag::must_not_insert, sqlpp::tag::must_not_update, sqlpp::tag::can_be_null>;
+    };
+    struct Name
+    {
+      struct _name_t
+      {
+        static constexpr const char* _get_name() { return "name"; }
+        template<typename T>
+        struct _member_t
+          {
+            T name;
+            T& operator()() { return name; }
+            const T& operator()() const { return name; }
+          };
+      };
+      using _traits = sqlpp::make_traits<sqlpp::varchar, sqlpp::tag::require_insert>;
+    };
+    struct Feature
+    {
+      struct _name_t
+      {
+        static constexpr const char* _get_name() { return "feature"; }
+        template<typename T>
+        struct _member_t
+          {
+            T feature;
+            T& operator()() { return feature; }
+            const T& operator()() const { return feature; }
+          };
+      };
+      using _traits = sqlpp::make_traits<sqlpp::integer, sqlpp::tag::require_insert>;
+    };
+  }
+
+  struct TabPerson: sqlpp::table_t<TabPerson,
+               TabPerson_::Id,
+               TabPerson_::Name,
+               TabPerson_::Feature>
+  {
+    struct _name_t
+    {
+      static constexpr const char* _get_name() { return "tab_person"; }
+      template<typename T>
+      struct _member_t
+      {
+        T tabPerson;
+        T& operator()() { return tabPerson; }
+        const T& operator()() const { return tabPerson; }
+      };
+    };
+  };
+  namespace TabFeature_
+  {
+    struct Id
+    {
+      struct _name_t
+      {
+        static constexpr const char* _get_name() { return "id"; }
+        template<typename T>
+        struct _member_t
+          {
+            T id;
+            T& operator()() { return id; }
+            const T& operator()() const { return id; }
+          };
+      };
+      using _traits = sqlpp::make_traits<sqlpp::integer, sqlpp::tag::must_not_insert, sqlpp::tag::must_not_update, sqlpp::tag::can_be_null>;
+    };
+    struct Name
+    {
+      struct _name_t
+      {
+        static constexpr const char* _get_name() { return "name"; }
+        template<typename T>
+        struct _member_t
+          {
+            T name;
+            T& operator()() { return name; }
+            const T& operator()() const { return name; }
+          };
+      };
+      using _traits = sqlpp::make_traits<sqlpp::varchar, sqlpp::tag::can_be_null>;
+    };
+    struct Fatal
+    {
+      struct _name_t
+      {
+        static constexpr const char* _get_name() { return "fatal"; }
+        template<typename T>
+        struct _member_t
+          {
+            T fatal;
+            T& operator()() { return fatal; }
+            const T& operator()() const { return fatal; }
+          };
+      };
+      using _traits = sqlpp::make_traits<sqlpp::boolean, sqlpp::tag::require_insert>;
+    };
+  }
+
+  struct TabFeature: sqlpp::table_t<TabFeature,
+               TabFeature_::Id,
+               TabFeature_::Name,
+               TabFeature_::Fatal>
+  {
+    struct _name_t
+    {
+      static constexpr const char* _get_name() { return "tab_feature"; }
+      template<typename T>
+      struct _member_t
+      {
+        T tabFeature;
+        T& operator()() { return tabFeature; }
+        const T& operator()() const { return tabFeature; }
+      };
+    };
+  };
+}
+#endif

examples/TabSample.h

@@ -0,0 +1,177 @@
+/*
+ * Copyright (c) 2013-2014, Roland Bock
+ * All rights reserved.
+ * 
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ * 
+ *   Redistributions of source code must retain the above copyright notice, this
+ *   list of conditions and the following disclaimer.
+ * 
+ *   Redistributions in binary form must reproduce the above copyright notice, this
+ *   list of conditions and the following disclaimer in the documentation and/or
+ *   other materials provided with the distribution.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
+ * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef SQLPP_TAB_SAMPLE_H
+#define SQLPP_TAB_SAMPLE_H
+
+#include <sqlpp11/table_base.h>
+#include <sqlpp11/column_types.h>
+
+
+namespace TabFoo_
+{
+	struct Omega
+	{
+		struct _name_t
+		{
+			static constexpr const char* _get_name() { return "omega"; }
+		};
+		template<typename T>
+		struct _member_t
+		{
+			/*
+			template<typename... TT>
+				_name_t(TT&&... t): omega(std::forward<TT>(t)...) {}
+
+			template<typename TT>
+				_name_t& operator=(TT&& t) { omega = std::forward<TT>(t); return *this; }
+				*/
+
+			T omega;
+		};
+		using _value_type = sqlpp::bigint;
+		struct _column_type
+		{
+		};
+	};
+}
+
+struct TabFoo: sqlpp::table_base_t<
+									TabFoo, 
+									TabFoo_::Omega
+													 >
+{
+	using _value_type = sqlpp::no_value_t;
+	struct _name_t
+	{
+		static constexpr const char* _get_name() { return "tab_foo"; }
+	};
+	template<typename T>
+		struct _member_t
+		{
+			T tabFoo;
+		};
+	template<typename Db>
+		void serialize(std::ostream& os, Db& db) const
+		{
+			os << _name_t::_get_name();
+		}
+};
+
+namespace TabSample_
+{
+	struct Alpha
+	{
+		struct _name_t
+		{
+			static constexpr const char* _get_name() { return "alpha"; }
+		};
+		template<typename T>
+		struct _member_t
+		{
+			/*
+			template<typename... TT>
+				_name_t(TT&&... t): alpha(std::forward<TT>(t)...) {}
+
+			template<typename TT>
+				_name_t& operator=(TT&& t) { alpha = std::forward<TT>(t); return *this; }
+				*/
+
+			T alpha;
+		};
+		using _value_type = sqlpp::bigint;
+		struct _column_type
+		{
+			using _must_not_insert = sqlpp::tag_yes;
+			using _must_not_update = sqlpp::tag_yes;
+			using _can_be_null = sqlpp::tag_yes;
+			using _foreign_key = decltype(TabFoo::omega);
+		};
+	};
+
+	struct Beta
+	{
+		struct _name_t
+		{
+			static constexpr const char* _get_name() { return "beta"; }
+		};
+		template<typename T>
+		struct _member_t
+		{
+			T beta;
+		};
+		using _value_type = sqlpp::varchar;
+		struct _column_type
+		{
+			using _can_be_null = sqlpp::tag_yes;
+			using _must_not_update = sqlpp::tag_yes;
+		};
+	};
+
+	struct Gamma
+	{
+		struct _name_t
+		{
+			static constexpr const char* _get_name() { return "gamma"; }
+		};
+		template<typename T>
+		struct _member_t
+		{
+			T gamma;
+		};
+		using _value_type = sqlpp::boolean;
+		struct _column_type
+		{
+			using _require_insert = sqlpp::tag_yes;
+		};
+	};
+}
+
+struct TabSample: sqlpp::table_base_t<
+									TabSample, 
+									TabSample_::Alpha, 
+									TabSample_::Beta,
+									TabSample_::Gamma
+													 >
+{
+	using _value_type = sqlpp::no_value_t;
+	struct _name_t
+	{
+		static constexpr const char* _get_name() { return "tab_sample"; }
+	};
+	template<typename T>
+		struct _member_t
+		{
+			T tabSample;
+		};
+	template<typename Db>
+		void serialize(std::ostream& os, Db& db) const
+		{
+			os << _name_t::_get_name();
+		}
+};
+
+#endif

examples/insert.cpp

@@ -0,0 +1,67 @@
+/*
+ * Copyright (c) 2014, Roland Bock
+ * All rights reserved.
+ * 
+ * Redistribution and use in source and binary forms, with or without modification, 
+ * are permitted provided that the following conditions are met:
+ * 
+ *  * Redistributions of source code must retain the above copyright notice, 
+ *    this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright notice, 
+ *    this list of conditions and the following disclaimer in the documentation 
+ *    and/or other materials provided with the distribution.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND 
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 
+ * IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE 
+ * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "Sample.h"
+#include "MockDb.h"
+#include <sqlpp11/sqlpp11.h>
+
+MockDb db;
+
+test::TabPerson p;
+test::TabFeature f;
+
+int main()
+{
+	db(insert_into(f).set(f.name = "loves c++", f.fatal = false));
+
+	//db(insert_into(f).set(f.nahme = "loves c++", f.fatal = false));
+
+	//db(insert_into(f).set(f.name == "loves c++", f.fatal = false));
+
+	//db(insert_into(f).set(f.name = "loves c++", f.fatal = "false"));
+
+	//db(insert_into(p).set(f.name = "loves c++", f.fatal = false));
+
+	//db(insert_into(f).set(f.name = "loves c++", p.feature = 7));
+
+	//db(insert_into(f).set(f.id = 42, f.name = "loves c++", f.fatal = false));
+	
+	//db(insert_into(f).set(f.name = "loves c++"));
+	
+
+	db(insert_into(f).default_values());
+
+	auto i = insert_into(p).columns(p.name, p.feature);
+	i.values.add(p.name = "Roland", p.feature = 1);
+	i.values.add(p.name = "Zaphod", p.feature = sqlpp::default_value);
+	db(i);
+
+
+	auto pi = db.prepare(insert_into(p).set(p.name = parameter(f.name), p.feature = parameter(p.feature)));
+	pi.params.name = "likes java";
+	pi.params.feature = true;
+
+	db(pi);
+}

examples/remove.cpp

@@ -0,0 +1,40 @@
+/*
+ * Copyright (c) 2014, Roland Bock
+ * All rights reserved.
+ * 
+ * Redistribution and use in source and binary forms, with or without modification, 
+ * are permitted provided that the following conditions are met:
+ * 
+ *  * Redistributions of source code must retain the above copyright notice, 
+ *    this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright notice, 
+ *    this list of conditions and the following disclaimer in the documentation 
+ *    and/or other materials provided with the distribution.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND 
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 
+ * IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE 
+ * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "Sample.h"
+#include "MockDb.h"
+#include <sqlpp11/sqlpp11.h>
+
+MockDb db;
+
+test::TabPerson p;
+test::TabFeature q;
+
+int main()
+{
+	db(remove_from(p)
+			.using_(p, q)
+			.where(p.feature == q.id and q.fatal == true));
+}

examples/sample.cpp

@@ -0,0 +1,59 @@
+/*
+ * Copyright (c) 2014, Roland Bock
+ * All rights reserved.
+ * 
+ * Redistribution and use in source and binary forms, with or without modification, 
+ * are permitted provided that the following conditions are met:
+ * 
+ *  * Redistributions of source code must retain the above copyright notice, 
+ *    this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright notice, 
+ *    this list of conditions and the following disclaimer in the documentation 
+ *    and/or other materials provided with the distribution.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND 
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 
+ * IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE 
+ * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "Sample.h"
+#include "MockDb.h"
+#include <sqlpp11/sqlpp11.h>
+
+MockDb db;
+
+test::TabPerson p;
+test::TabFeature f;
+
+int main()
+{
+	db(insert_into(f).set(f.name = "Loves C++", p.fatal = false));
+
+	db(insert_into(f).set(p.name = "Roland", p.feature = 1));
+
+	auto s = select(all_of(p))
+				      .from(p, q)
+						  .where(p.name == any(select(q.name)
+										               .from(q)
+																	 .where(true)))
+							.group_by(q.name)
+							.having(p.name.like("%Bee%"))
+							.order_by(p.name.asc())
+							.limit(3).offset(7);
+
+	auto x = s.as(sqlpp::alias::x);
+	for (const auto& row : db(select(p.id, x.name)
+				.from(p.join(x).on(p.feature == x.feature))
+				.where(true)))
+	{
+		int id = row.id;
+		std::string name = row.name;
+	}
+}

examples/sample.sql

@@ -0,0 +1,40 @@
+/*
+ * Copyright (c) 2013, Roland Bock
+ * All rights reserved.
+ * 
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ * 
+ *   Redistributions of source code must retain the above copyright notice, this
+ *   list of conditions and the following disclaimer.
+ * 
+ *   Redistributions in binary form must reproduce the above copyright notice, this
+ *   list of conditions and the following disclaimer in the documentation and/or
+ *   other materials provided with the distribution.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
+ * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+CREATE TABLE tab_person
+(
+    id int AUTO_INCREMENT PRIMARY KEY,
+    name varchar(255) NOT NULL,
+    feature int NOT NULL
+);
+
+CREATE TABLE tab_feature
+(
+    id int AUTO_INCREMENT PRIMARY KEY,
+    name varchar(255) NULL DEFAULT "",
+    fatal bool NOT NULL
+);
+

examples/select.cpp

@@ -0,0 +1,135 @@
+/*
+ * Copyright (c) 2014, Roland Bock
+ * All rights reserved.
+ * 
+ * Redistribution and use in source and binary forms, with or without modification, 
+ * are permitted provided that the following conditions are met:
+ * 
+ *  * Redistributions of source code must retain the above copyright notice, 
+ *    this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright notice, 
+ *    this list of conditions and the following disclaimer in the documentation 
+ *    and/or other materials provided with the distribution.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND 
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 
+ * IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE 
+ * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#if defined(__clang__)
+#pragma clang diagnostic ignored "-Wunused-variable"
+#endif
+#if defined(__GNUC__)
+#pragma GCC diagnostic ignored "-Wunused-variable"
+#endif
+
+#include "Sample.h"
+#include "MockDb.h"
+#include <sqlpp11/sqlpp11.h>
+
+SQLPP_ALIAS_PROVIDER(cheesecake);
+
+MockDb db;
+
+test::TabPerson p;
+test::TabFeature f;
+
+int main()
+{
+	for (const auto& row : db(select(all_of(p)).from(p).where(p.id > 7)))
+	{
+		int64_t id = row.id;
+		std::string name = row.name;
+		int64_t feature = row.feature;
+	}
+
+
+#if	0
+	for (const auto& row : db(select(p.name).from(p).where(p.name.like("Herb%"))))
+	{
+		int64_t id = row.id;
+		std::string name = row.name;
+		int64_t feature = row.feature;
+	}
+#endif
+
+
+
+#if 0
+	for (const auto& row : db(select(p.name, f.name.as(cheesecake)).from(p,f).where(p.id > 7 and p.feature == 3)))
+	{
+		//int64_t id = row.id;
+		//std::string a = row.a;
+		std::string name = row.name;
+		std::string feature = row.cheesecake;
+	}
+#endif
+
+
+
+#if 0
+	for (const auto& row : db(select(multi_column(all_of(p)).as(p), multi_column(f.name, f.id).as(f)).from(p,f).where(true)))
+	{
+		//int64_t id = row.id;
+		//std::string a = row.a;
+		std::string name = row.tabPerson.name;
+		std::string name1 = row.tabFeature.name;
+		//int64_t feature = row.feature;
+	}
+#endif
+	
+	
+	
+	
+	
+	
+
+#if !0
+	auto s = select(all_of(p)) 
+				      .from(p, f)
+						  .where(p.name == any(select(f.name)
+										               .from(f)
+																	 .where(true)))
+							.group_by(f.name)
+							.having(p.name.like("%Bee%"))
+							.order_by(p.name.asc())
+							.limit(3).offset(7);
+
+	auto x = s.as(sqlpp::alias::x);
+	for (const auto& row : db(select(p.id, x.name)
+				.from(p.join(x).on(p.feature == x.feature))
+				.where(true)))
+	{
+		int id = row.id;
+		std::string name = row.name;
+	}
+#endif
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+}

examples/update.cpp

@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) 2014, Roland Bock
+ * All rights reserved.
+ * 
+ * Redistribution and use in source and binary forms, with or without modification, 
+ * are permitted provided that the following conditions are met:
+ * 
+ *  * Redistributions of source code must retain the above copyright notice, 
+ *    this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright notice, 
+ *    this list of conditions and the following disclaimer in the documentation 
+ *    and/or other materials provided with the distribution.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND 
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 
+ * IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE 
+ * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "Sample.h"
+#include "MockDb.h"
+#include <sqlpp11/sqlpp11.h>
+
+MockDb db;
+
+test::TabPerson p;
+test::TabFeature q;
+
+int main()
+{
+	db(update(p).set(p.feature = 7).where(p.id == 23));
+}

include/sqlpp11/alias.h

@@ -35,7 +35,7 @@ namespace sqlpp
 	template<typename Expression, typename AliasProvider>
 		struct expression_alias_t
 		{
-			using _traits = make_traits<value_type_of<Expression>, tag::is_named_expression, tag::is_alias>;
+			using _traits = make_traits<value_type_of<Expression>, tag::is_selectable, tag::is_alias>;
 			using _recursive_traits = make_recursive_traits<Expression>;
 
 			static_assert(is_expression_t<Expression>::value, "invalid argument for an expression alias");

include/sqlpp11/all_of.h

@@ -41,7 +41,7 @@ namespace sqlpp
 			template<typename AliasProvider>
 				detail::copy_tuple_args_t<multi_column_alias_t, AliasProvider, _column_tuple_t> as(const AliasProvider& alias)
 				{
-					return ::sqlpp::multi_column(_column_tuple_t{}).as(alias);
+					return multi_column(_column_tuple_t{}).as(alias);
 				}
 		};
 

include/sqlpp11/any.h

@@ -35,7 +35,7 @@ namespace sqlpp
 	template<typename Select>
 		struct any_t
 		{
-			using _traits = make_traits<value_type_of<Select>, ::sqlpp::tag::is_multi_expression>;
+			using _traits = make_traits<value_type_of<Select>, tag::is_multi_expression>;
 			using _recursive_traits = make_recursive_traits<Select>;
 
 			struct _name_t

include/sqlpp11/assignment.h

@@ -40,7 +40,7 @@ namespace sqlpp
 	template<typename Lhs, typename Rhs>
 		struct assignment_t
 		{
-			using _traits = make_traits<no_value_t, ::sqlpp::tag::is_assignment>;
+			using _traits = make_traits<no_value_t, tag::is_assignment>;
 			using _recursive_traits = make_recursive_traits<Lhs, Rhs>;
 
 			using _lhs_t = Lhs;

include/sqlpp11/avg.h

@@ -32,13 +32,14 @@
 namespace sqlpp
 {
 	template<typename Flag, typename Expr>
-		struct avg_t: public floating_point::template expression_operators<avg_t<Flag, Expr>>,
+		struct avg_t:
+			public expression_operators<avg_t<Flag, Expr>, floating_point>,
 			public alias_operators<avg_t<Flag, Expr>>
 	{
-		using _traits = make_traits<floating_point, ::sqlpp::tag::is_expression, ::sqlpp::tag::is_named_expression>;
-		using _recursive_traits = make_recursive_traits<Expr>;
+		using _traits = make_traits<floating_point, tag::is_expression, tag::is_selectable>;
+		using _recursive_traits = make_recursive_traits<Expr, aggregate_function>;
 
-		static_assert(is_noop<Flag>::value or std::is_same<sqlpp::distinct_t, Flag>::value, "avg() used with flag other than 'distinct'");
+		static_assert(is_noop<Flag>::value or std::is_same<distinct_t, Flag>::value, "avg() used with flag other than 'distinct'");
 		static_assert(is_numeric_t<Expr>::value, "avg() requires a value expression as argument");
 
 		struct _name_t
@@ -74,7 +75,7 @@ namespace sqlpp
 			static Context& _(const T& t, Context& context)
 			{
 				context << "AVG(";
-				if (std::is_same<sqlpp::distinct_t, Flag>::value)
+				if (std::is_same<distinct_t, Flag>::value)
 				{
 					serialize(Flag(), context);
 					context << ' ';
@@ -88,13 +89,15 @@ namespace sqlpp
 	template<typename T>
 		auto avg(T t) -> avg_t<noop, wrap_operand_t<T>>
 		{
+			static_assert(not contains_aggregate_function_t<wrap_operand_t<T>>::value, "avg() cannot be used on an aggregate function");
 			static_assert(is_numeric_t<wrap_operand_t<T>>::value, "avg() requires a value expression as argument");
 			return { t };
 		}
 
 	template<typename T>
-		auto avg(const sqlpp::distinct_t&, T t) -> avg_t<sqlpp::distinct_t, wrap_operand_t<T>>
+		auto avg(const distinct_t&, T t) -> avg_t<distinct_t, wrap_operand_t<T>>
 		{
+			static_assert(not contains_aggregate_function_t<wrap_operand_t<T>>::value, "avg() cannot be used on an aggregate function");
 			static_assert(is_numeric_t<wrap_operand_t<T>>::value, "avg() requires a value expression as argument");
 			return { t };
 		}

include/sqlpp11/basic_expression_operators.h

@@ -27,18 +27,19 @@
 #ifndef SQLPP_DETAIL_BASIC_EXPRESSION_OPERATORS_H
 #define SQLPP_DETAIL_BASIC_EXPRESSION_OPERATORS_H
 
+#include <sqlpp11/value_type_fwd.h>
 #include <sqlpp11/alias.h>
 #include <sqlpp11/sort_order.h>
 #include <sqlpp11/expression_fwd.h>
 #include <sqlpp11/in_fwd.h>
 #include <sqlpp11/is_null_fwd.h>
-#include <sqlpp11/wrap_operand.h>
+#include <sqlpp11/wrap_operand_fwd.h>
 #include <sqlpp11/detail/logic.h>
 
 namespace sqlpp
 {
 	// basic operators
-	template<typename Base, template<typename> class IsCorrectValueType>
+	template<typename Expr, typename ValueType>
 		struct basic_expression_operators
 		{
 			template<typename T>
@@ -47,107 +48,107 @@ namespace sqlpp
 					static constexpr bool value = 
 						(is_expression_t<T>::value // expressions are OK
 						 or is_multi_expression_t<T>::value) // multi-expressions like ANY are OK for comparisons, too
-						and IsCorrectValueType<T>::value // the correct value type is required, of course
+						and ValueType::template _is_valid_operand<T>::value // the correct value type is required, of course
 						;
 				};
 
 			template<typename T>
-				equal_to_t<Base, wrap_operand_t<T>> operator==(T t) const
+				equal_to_t<Expr, wrap_operand_t<T>> operator==(T t) const
 				{
 					using rhs = wrap_operand_t<T>;
 					static_assert(_is_valid_comparison_operand<rhs>::value, "invalid rhs operand in comparison");
 
-					return { *static_cast<const Base*>(this), {rhs{t}} };
+					return { *static_cast<const Expr*>(this), {rhs{t}} };
 				}
 
 			template<typename T>
-				not_equal_to_t<Base, wrap_operand_t<T>> operator!=(T t) const
+				not_equal_to_t<Expr, wrap_operand_t<T>> operator!=(T t) const
 				{
 					using rhs = wrap_operand_t<T>;
 					static_assert(_is_valid_comparison_operand<rhs>::value, "invalid rhs operand in comparison");
 
-					return { *static_cast<const Base*>(this), {rhs{t}} };
+					return { *static_cast<const Expr*>(this), {rhs{t}} };
 				}
 
 			template<typename T>
-				less_than_t<Base, wrap_operand_t<T>> operator<(T t) const
+				less_than_t<Expr, wrap_operand_t<T>> operator<(T t) const
 				{
 					using rhs = wrap_operand_t<T>;
 					static_assert(_is_valid_comparison_operand<rhs>::value, "invalid rhs operand in comparison");
 
-					return { *static_cast<const Base*>(this), rhs{t} };
+					return { *static_cast<const Expr*>(this), rhs{t} };
 				}
 
 			template<typename T>
-				less_equal_t<Base, wrap_operand_t<T>> operator<=(T t) const
+				less_equal_t<Expr, wrap_operand_t<T>> operator<=(T t) const
 				{
 					using rhs = wrap_operand_t<T>;
 					static_assert(_is_valid_comparison_operand<rhs>::value, "invalid rhs operand in comparison");
 
-					return { *static_cast<const Base*>(this), rhs{t} };
+					return { *static_cast<const Expr*>(this), rhs{t} };
 				}
 
 			template<typename T>
-				greater_than_t<Base, wrap_operand_t<T>> operator>(T t) const
+				greater_than_t<Expr, wrap_operand_t<T>> operator>(T t) const
 				{
 					using rhs = wrap_operand_t<T>;
 					static_assert(_is_valid_comparison_operand<rhs>::value, "invalid rhs operand in comparison");
 
-					return { *static_cast<const Base*>(this), rhs{t} };
+					return { *static_cast<const Expr*>(this), rhs{t} };
 				}
 
 			template<typename T>
-				greater_equal_t<Base, wrap_operand_t<T>> operator>=(T t) const
+				greater_equal_t<Expr, wrap_operand_t<T>> operator>=(T t) const
 				{
 					using rhs = wrap_operand_t<T>;
 					static_assert(_is_valid_comparison_operand<rhs>::value, "invalid rhs operand in comparison");
 
-					return { *static_cast<const Base*>(this), rhs{t} };
+					return { *static_cast<const Expr*>(this), rhs{t} };
 				}
 
-			is_null_t<true, Base> is_null() const
+			is_null_t<true, Expr> is_null() const
 			{
-				return { *static_cast<const Base*>(this) };
+				return { *static_cast<const Expr*>(this) };
 			}
 
-			is_null_t<false, Base> is_not_null() const
+			is_null_t<false, Expr> is_not_null() const
 			{
-				return { *static_cast<const Base*>(this) };
+				return { *static_cast<const Expr*>(this) };
 			}
 
-			sort_order_t<Base, sort_type::asc> asc()
+			sort_order_t<Expr, sort_type::asc> asc() const
 			{ 
-				return { *static_cast<const Base*>(this) };
+				return { *static_cast<const Expr*>(this) };
 			}
 
-			sort_order_t<Base, sort_type::desc> desc()
+			sort_order_t<Expr, sort_type::desc> desc() const
 			{ 
-				return { *static_cast<const Base*>(this) };
+				return { *static_cast<const Expr*>(this) };
 			}
 
 			// Hint: use value_list wrapper for containers...
 			template<typename... T>
-				in_t<true, Base, wrap_operand_t<T>...> in(T... t) const
+				in_t<true, Expr, wrap_operand_t<T>...> in(T... t) const
 				{
 					static_assert(detail::all_t<_is_valid_comparison_operand<wrap_operand_t<T>>::value...>::value, "at least one operand of in() is not valid");
-					return { *static_cast<const Base*>(this), wrap_operand_t<T>{t}... };
+					return { *static_cast<const Expr*>(this), wrap_operand_t<T>{t}... };
 				}
 
 			template<typename... T>
-				in_t<false, Base, wrap_operand_t<T>...> not_in(T... t) const
+				in_t<false, Expr, wrap_operand_t<T>...> not_in(T... t) const
 				{
 					static_assert(detail::all_t<_is_valid_comparison_operand<wrap_operand_t<T>>::value...>::value, "at least one operand of in() is not valid");
-					return { *static_cast<const Base*>(this), wrap_operand_t<T>{t}... };
+					return { *static_cast<const Expr*>(this), wrap_operand_t<T>{t}... };
 				}
 		};
 
-	template<typename Base>
+	template<typename Expr>
 		struct alias_operators
 		{
 			template<typename alias_provider>
-				expression_alias_t<Base, alias_provider> as(const alias_provider&)
+				expression_alias_t<Expr, alias_provider> as(const alias_provider&) const
 				{
-					return { *static_cast<const Base*>(this) };
+					return { *static_cast<const Expr*>(this) };
 				}
 		};
 

include/sqlpp11/boolean.h

@@ -40,32 +40,39 @@ namespace sqlpp
 	// boolean value type
 	struct boolean
 	{
-		using _traits = make_traits<boolean, ::sqlpp::tag::is_boolean, ::sqlpp::tag::is_value_type>;
-		using _tag = ::sqlpp::tag::is_boolean;
+		using _traits = make_traits<boolean, tag::is_value_type>;
+		using _tag = tag::is_boolean;
 		using _cpp_value_type = bool;
 
-		struct _parameter_t
+		template<typename T>
+			using _is_valid_operand = is_boolean_t<T>;
+	};
+
+	// boolean parameter type
+	template<>
+		struct parameter_value_t<boolean>
 		{
 			using _value_type = boolean; // FIXME
+			using _cpp_value_type = typename _value_type::_cpp_value_type;
 
-			_parameter_t():
+			parameter_value_t():
 				_value(false),
 				_is_null(true)
 			{}
 
-			_parameter_t(const _cpp_value_type& value):
+			parameter_value_t(const _cpp_value_type& value):
 				_value(value),
 				_is_null(false)
 			{}
 
-			_parameter_t& operator=(const _cpp_value_type& value)
+			parameter_value_t& operator=(const _cpp_value_type& value)
 			{
 				_value = value;
 				_is_null = false;
 				return *this;
 			}
 
-			_parameter_t& operator=(const tvin_t<wrap_operand_t<_cpp_value_type>>& t)
+			parameter_value_t& operator=(const tvin_t<wrap_operand_t<_cpp_value_type>>& t)
 			{
 				if (t._is_trivial())
 				{
@@ -80,7 +87,7 @@ namespace sqlpp
 				return *this;
 			}
 
-			_parameter_t& operator=(const std::nullptr_t&)
+			parameter_value_t& operator=(const std::nullptr_t&)
 			{
 				_value = false;
 				_is_null = true;
@@ -110,18 +117,13 @@ namespace sqlpp
 			bool _is_null;
 		};
 
-		template<typename T>
-			struct _is_valid_operand
-			{
-				static constexpr bool value = 
-					is_expression_t<T>::value // expressions are OK
-					and is_boolean_t<T>::value // the correct value type is required, of course
-					;
-			};
-
+	// boolean expression operators
 	template<typename Base>
-			struct expression_operators: public basic_expression_operators<Base, is_boolean_t>
+		struct expression_operators<Base, boolean>: public basic_expression_operators<Base, boolean>
 	{
+		template<typename T>
+			using _is_valid_operand = is_valid_operand<boolean, T>;
+
 		template<typename T>
 			logical_and_t<Base, wrap_operand_t<T>> operator and(T t) const
 			{
@@ -146,12 +148,13 @@ namespace sqlpp
 		}
 	};
 
+	// boolean column operators
 	template<typename Base>
-			struct column_operators
+		struct column_operators<Base, boolean>
 		{
 		};
-	};
 
+	// boolean result field
 	template<typename Db, typename FieldSpec>
 		struct result_field_t<boolean, Db, FieldSpec>: public result_field_methods_t<result_field_t<boolean, Db, FieldSpec>>
 	{

include/sqlpp11/boolean_expression.h

@@ -33,7 +33,7 @@
 namespace sqlpp
 {
 	template<typename Database>
-		struct boolean_expression_t: public boolean::template expression_operators<boolean_expression_t<Database>>
+		struct boolean_expression_t: public expression_operators<boolean_expression_t<Database>, boolean>
 		{
 			using _traits = make_traits<boolean, tag::is_expression>;
 			using _recursive_traits = make_recursive_traits<>;

include/sqlpp11/column.h

@@ -42,13 +42,14 @@
 namespace sqlpp
 {
 	template<typename Table, typename ColumnSpec>
-		struct column_t: public value_type_of<ColumnSpec>::template expression_operators<column_t<Table, ColumnSpec>>,
-		public value_type_of<ColumnSpec>::template column_operators<column_t<Table, ColumnSpec>>
+		struct column_t: 
+			public expression_operators<column_t<Table, ColumnSpec>, value_type_of<ColumnSpec>>,
+			public column_operators<column_t<Table, ColumnSpec>, value_type_of<ColumnSpec>>
 	{ 
 		struct _traits
 		{
 			using _value_type = value_type_of<ColumnSpec>;
-			using _tags = detail::make_joined_set_t<detail::type_set<tag::is_column, tag::is_expression, tag::is_named_expression>, typename ColumnSpec::_traits::_tags>;
+			using _tags = detail::make_joined_set_t<detail::type_set<tag::is_column, tag::is_expression, tag::is_selectable>, typename ColumnSpec::_traits::_tags>;
 		};
 
 		struct _recursive_traits
@@ -58,7 +59,9 @@ namespace sqlpp
 			using _provided_outer_tables = detail::type_set<>;
 			using _required_tables = detail::type_set<Table>;
 			using _extra_tables = detail::type_set<>;
-			using _can_be_null = column_spec_can_be_null_t<ColumnSpec>;
+			using _tags = typename std::conditional<column_spec_can_be_null_t<ColumnSpec>::value,
+									detail::type_set<tag::can_be_null>,
+									detail::type_set<>>::type;
 		};
 
 		using _spec_t = ColumnSpec;
@@ -66,7 +69,7 @@ namespace sqlpp
 		using _name_t = typename _spec_t::_name_t;
 
 		template<typename T>
-			using _is_valid_operand = typename value_type_of<ColumnSpec>::template _is_valid_operand<T>;
+			using _is_valid_operand = is_valid_operand<value_type_of<ColumnSpec>, T>;
 
 		column_t() = default;
 		column_t(const column_t&) = default;
@@ -90,22 +93,22 @@ namespace sqlpp
 			auto operator =(T t) const -> assignment_t<column_t, wrap_operand_t<T>>
 			{
 				using rhs = wrap_operand_t<T>;
-				static_assert(_is_valid_operand<rhs>::value, "invalid rhs operand assignment operand");
+				static_assert(_is_valid_operand<rhs>::value, "invalid rhs assignment operand");
 
 				return { *this, {rhs{t}} };
 			}
 
-		auto operator =(sqlpp::null_t) const
-			->assignment_t<column_t, sqlpp::null_t>
+		auto operator =(null_t) const
+			->assignment_t<column_t, null_t>
 			{
 				static_assert(can_be_null_t<column_t>::value, "column cannot be null");
-				return { *this, sqlpp::null_t{} };
+				return { *this, null_t{} };
 			}
 
-		auto operator =(sqlpp::default_value_t) const
-			->assignment_t<column_t, sqlpp::default_value_t>
+		auto operator =(default_value_t) const
+			->assignment_t<column_t, default_value_t>
 			{
-				return { *this, sqlpp::default_value_t{} };
+				return { *this, default_value_t{} };
 			}
 	};
 

include/sqlpp11/concat.h

@@ -36,14 +36,15 @@ namespace sqlpp
 {
 	// FIXME: Remove First, inherit from text_t
 	template<typename First, typename... Args>
-		struct concat_t: public value_type_of<First>::template expression_operators<concat_t<First, Args...>>,
+		struct concat_t: 
+			public expression_operators<concat_t<First, Args...>, value_type_of<First>>,
 			public alias_operators<concat_t<First, Args...>>
 	{
-		using _traits = make_traits<value_type_of<First>, ::sqlpp::tag::is_expression, ::sqlpp::tag::is_named_expression>;
+		using _traits = make_traits<value_type_of<First>, tag::is_expression, tag::is_selectable>;
 		using _recursive_traits = make_recursive_traits<First, Args...>;
 
 		static_assert(sizeof...(Args) > 0, "concat requires two arguments at least");
-		static_assert(sqlpp::detail::all_t<is_text_t<First>::value, is_text_t<Args>::value...>::value, "at least one non-text argument detected in concat()");
+		static_assert(detail::all_t<is_text_t<First>::value, is_text_t<Args>::value...>::value, "at least one non-text argument detected in concat()");
 		struct _name_t
 		{
 			static constexpr const char* _get_name() { return "CONCAT"; }

include/sqlpp11/count.h

@@ -33,14 +33,24 @@
 namespace sqlpp
 {
 	template<typename Flag, typename Expr>
-		struct count_t: public sqlpp::integral::template expression_operators<count_t<Flag, Expr>>,
+		struct count_t: 
+			public expression_operators<count_t<Flag, Expr>, integral>,
 			public alias_operators<count_t<Flag, Expr>>
 	{
-		using _traits = make_traits<::sqlpp::integral, ::sqlpp::tag::is_expression, ::sqlpp::tag::is_named_expression>;
-		using _recursive_traits = make_recursive_traits<Expr>;
+		using _traits = make_traits<integral, tag::is_expression, tag::is_selectable>;
+		struct _recursive_traits
+		{
+			using _required_tables = required_tables_of<Expr>;
+			using _provided_tables = provided_tables_of<Expr>;
+			using _provided_outer_tables = provided_outer_tables_of<Expr>;
+			using _extra_tables = extra_tables_of<Expr>;
+			using _parameters = parameters_of<Expr>;
+			using _tags = detail::make_difference_set_t<detail::joined_set_t<recursive_tags_of<Expr>, recursive_tags_of<aggregate_function>>, 
+						                                      detail::type_set<tag::can_be_null>>;
+		};
 
-		static_assert(is_noop<Flag>::value or std::is_same<sqlpp::distinct_t, Flag>::value, "count() used with flag other than 'distinct'");
-		static_assert(is_expression_t<Expr>::value, "count() requires a sql expression as argument");
+
+		static_assert(is_noop<Flag>::value or std::is_same<distinct_t, Flag>::value, "count() used with flag other than 'distinct'");
 
 		struct _name_t
 		{
@@ -75,7 +85,7 @@ namespace sqlpp
 			static Context& _(const T& t, Context& context)
 			{
 				context << "COUNT(";
-				if (std::is_same<sqlpp::distinct_t, Flag>::value)
+				if (std::is_same<distinct_t, Flag>::value)
 				{
 					serialize(Flag(), context);
 					context << ' ';
@@ -94,7 +104,7 @@ namespace sqlpp
 		}
 
 	template<typename T>
-		auto count(const sqlpp::distinct_t&, T t) -> count_t<sqlpp::distinct_t, wrap_operand_t<T>>
+		auto count(const distinct_t&, T t) -> count_t<distinct_t, wrap_operand_t<T>>
 		{
 			static_assert(is_expression_t<wrap_operand_t<T>>::value, "count() requires an expression as argument");
 			return { t };

include/sqlpp11/detail/copy_tuple_args.h

@@ -43,9 +43,9 @@ namespace sqlpp
 			};
 
 		template<typename T>
-			struct as_tuple<::sqlpp::all_of_t<T>>
+			struct as_tuple<all_of_t<T>>
 			{
-				static typename ::sqlpp::all_of_t<T>::_column_tuple_t _(::sqlpp::all_of_t<T>) { return { }; }
+				static typename all_of_t<T>::_column_tuple_t _(all_of_t<T>) { return { }; }
 			};
 
 		template<typename... Args>

include/sqlpp11/detail/logic.h

@@ -27,6 +27,7 @@
 #ifndef SQLPP_DETAIL_LOGIC_H
 #define SQLPP_DETAIL_LOGIC_H
 
+#include <ciso646> // Required for some compilers to use aliases for boolean operators
 #include <type_traits>
 
 namespace sqlpp

include/sqlpp11/detail/type_set.h

@@ -73,7 +73,7 @@ namespace sqlpp
 		template<typename E, typename SET>
 			struct is_element_of
 			{
-				static_assert(::sqlpp::wrong_t<is_element_of>::value, "SET has to be a type set");
+				static_assert(wrong_t<is_element_of>::value, "SET has to be a type set");
 			};
 
 		template<typename E, typename... Elements>
@@ -85,7 +85,7 @@ namespace sqlpp
 		template<typename L, typename R>
 			struct joined_set
 			{
-				static_assert(::sqlpp::wrong_t<joined_set>::value, "L and R have to be type sets");
+				static_assert(wrong_t<joined_set>::value, "L and R have to be type sets");
 			};
 
 		template<typename... LElements, typename... RElements>
@@ -100,7 +100,7 @@ namespace sqlpp
 		template<typename L, typename R>
 			struct is_superset_of
 			{
-				static_assert(::sqlpp::wrong_t<is_superset_of>::value, "L and R have to be type sets");
+				static_assert(wrong_t<is_superset_of>::value, "L and R have to be type sets");
 			};
 
 		template<typename... LElements, typename... RElements>
@@ -118,7 +118,7 @@ namespace sqlpp
 		template<typename L, typename R>
 			struct is_disjunct_from
 			{
-				static_assert(::sqlpp::wrong_t<is_disjunct_from>::value, "invalid argument for is_disjunct_from");
+				static_assert(wrong_t<is_disjunct_from>::value, "invalid argument for is_disjunct_from");
 			};
 
 		template<typename... LElements, typename... RElements>
@@ -174,7 +174,7 @@ namespace sqlpp
 		template<typename... T>
 			struct make_joined_set
 			{
-				static_assert(::sqlpp::wrong_t<make_joined_set>::value, "invalid argument for joined set");
+				static_assert(wrong_t<make_joined_set>::value, "invalid argument for joined set");
 			};
 
 		template<>
@@ -197,7 +197,7 @@ namespace sqlpp
 		template<typename Minuend, typename Subtrahend>
 			struct make_difference_set
 			{
-				static_assert(::sqlpp::wrong_t<make_difference_set>::value, "invalid argument for difference set");
+				static_assert(wrong_t<make_difference_set>::value, "invalid argument for difference set");
 			};
 
 		template<typename... Minuends, typename... Subtrahends>
@@ -214,7 +214,7 @@ namespace sqlpp
 		template<typename Lhs, typename Rhs>
 			struct make_intersect_set
 			{
-				static_assert(::sqlpp::wrong_t<make_intersect_set>::value, "invalid argument for intersect set");
+				static_assert(wrong_t<make_intersect_set>::value, "invalid argument for intersect set");
 			};
 
 		template<typename... LhsElements, typename... RhsElements>
@@ -232,7 +232,7 @@ namespace sqlpp
 		template<template<typename> class Transformation, typename T>
 			struct transform_set
 			{
-				static_assert(::sqlpp::wrong_t<transform_set>::value, "invalid argument for transform_set");
+				static_assert(wrong_t<transform_set>::value, "invalid argument for transform_set");
 			};
 
 		template<template<typename> class Transformation, typename... E>

include/sqlpp11/eval.h

@@ -0,0 +1,62 @@
+/*
+ * Copyright (c) 2013-2014, Roland Bock
+ * All rights reserved.
+ * 
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ * 
+ *   Redistributions of source code must retain the above copyright notice, this
+ *   list of conditions and the following disclaimer.
+ * 
+ *   Redistributions in binary form must reproduce the above copyright notice, this
+ *   list of conditions and the following disclaimer in the documentation and/or
+ *   other materials provided with the distribution.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
+ * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef SQLPP_EVAL_H
+#define SQLPP_EVAL_H
+
+#include <sqlpp11/type_traits.h>
+#include <sqlpp11/field_spec.h>
+#include <sqlpp11/alias_provider.h>
+#include <sqlpp11/verbatim.h>
+
+namespace sqlpp
+{
+	template<typename Db, typename Expr>
+		struct eval_t
+		{
+			static_assert(is_database<Db>::value, "Db parameter of eval has to be a database connection");
+			static_assert(is_expression_t<Expr>::value, "Expression parameter of eval has to be an sqlpp expression or a string");
+			static_assert(required_tables_of<Expr>::size::value == 0, "Expression cannot be used in eval because it requires tables");
+			using _name_type = alias::a_t::_name_t;
+			using _value_type = value_type_of<Expr>;
+			using _field_spec = field_spec_t<_name_type, _value_type, true, false>;
+			using type = result_field_t<_value_type, Db, _field_spec>;
+		};
+
+	template<typename Db, typename Expr, typename std::enable_if<not std::is_convertible<Expr, std::string>::value, int>::type = 0>
+		auto eval(Db& db, Expr expr) -> typename eval_t<Db, Expr>::type
+		{
+			return db(select(expr.as(alias::a))).front().a;
+		}
+
+	template<typename ValueType, typename Db>
+		auto eval(Db& db, std::string sql_code) -> decltype(eval(db, verbatim<ValueType>(sql_code)))
+		{
+			return eval(db, verbatim<ValueType>(sql_code));
+		}
+}
+
+#endif

include/sqlpp11/exists.h

@@ -32,10 +32,11 @@
 namespace sqlpp
 {
 	template<typename Select>
-		struct exists_t: public boolean::template expression_operators<exists_t<Select>>,
+		struct exists_t: 
+			public expression_operators<exists_t<Select>, boolean>,
 			public alias_operators<exists_t<Select>>
 	{
-		using _traits = make_traits<boolean, ::sqlpp::tag::is_expression, ::sqlpp::tag::is_named_expression>;
+		using _traits = make_traits<boolean, tag::is_expression, tag::is_selectable>;
 		using _recursive_traits = make_recursive_traits<Select>;
 
 		static_assert(is_select_t<Select>::value, "exists() requires a select expression as argument");

include/sqlpp11/expression.h

@@ -39,10 +39,11 @@
 namespace sqlpp
 {
 	template<typename Lhs, typename Rhs>
-		struct binary_expression_t<Lhs, op::equal_to, Rhs>: public ::sqlpp::boolean::template expression_operators<binary_expression_t<Lhs, op::equal_to, Rhs>>,
+		struct binary_expression_t<Lhs, op::equal_to, Rhs>:
+			public expression_operators<binary_expression_t<Lhs, op::equal_to, Rhs>, boolean>,
 			public alias_operators<binary_expression_t<Lhs, op::equal_to, Rhs>>
 		{
-			using _traits = make_traits<boolean, sqlpp::tag::is_expression>;
+			using _traits = make_traits<boolean, tag::is_expression>;
 			using _recursive_traits = make_recursive_traits<Lhs, Rhs>;
 			using _lhs_t = Lhs;
 			using _rhs_t = rhs_wrap_t<allow_tvin_t<Rhs>, trivial_value_is_null_t<_lhs_t>::value>;
@@ -86,10 +87,11 @@ namespace sqlpp
 		};
 
 	template<typename Lhs, typename Rhs>
-		struct binary_expression_t<Lhs, op::not_equal_to, Rhs>: public ::sqlpp::boolean::template expression_operators<binary_expression_t<Lhs, op::not_equal_to, Rhs>>,
+		struct binary_expression_t<Lhs, op::not_equal_to, Rhs>:
+			public expression_operators<binary_expression_t<Lhs, op::not_equal_to, Rhs>, boolean>,
 			public alias_operators<binary_expression_t<Lhs, op::not_equal_to, Rhs>>
 		{
-			using _traits = make_traits<boolean, sqlpp::tag::is_expression>;
+			using _traits = make_traits<boolean, tag::is_expression>;
 			using _recursive_traits = make_recursive_traits<Lhs, Rhs>;
 			using _lhs_t = Lhs;
 			using _rhs_t = rhs_wrap_t<allow_tvin_t<Rhs>, trivial_value_is_null_t<_lhs_t>::value>;
@@ -133,10 +135,11 @@ namespace sqlpp
 		};
 
 	template<typename Rhs>
-		struct unary_expression_t<op::logical_not, Rhs>: public ::sqlpp::boolean::template expression_operators<unary_expression_t<op::logical_not, Rhs>>,
+		struct unary_expression_t<op::logical_not, Rhs>:
+			public expression_operators<unary_expression_t<op::logical_not, Rhs>, boolean>,
 			public alias_operators<unary_expression_t<op::logical_not, Rhs>>
 		{
-			using _traits = make_traits<boolean, sqlpp::tag::is_expression>;
+			using _traits = make_traits<boolean, tag::is_expression>;
 			using _recursive_traits = make_recursive_traits<Rhs>;
 
 			unary_expression_t(Rhs rhs):
@@ -177,10 +180,11 @@ namespace sqlpp
 		};
 
 	template<typename Lhs, typename O, typename Rhs>
-		struct binary_expression_t: public value_type_of<O>::template expression_operators<binary_expression_t<Lhs, O, Rhs>>,
+		struct binary_expression_t:
+			public expression_operators<binary_expression_t<Lhs, O, Rhs>, value_type_of<O>>,
 			public alias_operators<binary_expression_t<Lhs, O, Rhs>>
 	{
-		using _traits = make_traits<value_type_of<O>, sqlpp::tag::is_expression>;
+		using _traits = make_traits<value_type_of<O>, tag::is_expression>;
 		using _recursive_traits = make_recursive_traits<Lhs, Rhs>;
 
 		binary_expression_t(Lhs lhs, Rhs rhs):
@@ -215,10 +219,11 @@ namespace sqlpp
 		};
 
 	template<typename O, typename Rhs>
-		struct unary_expression_t: public value_type_of<O>::template expression_operators<unary_expression_t<O, Rhs>>,
+		struct unary_expression_t:
+			public expression_operators<unary_expression_t<O, Rhs>, value_type_of<O>>,
 			public alias_operators<unary_expression_t<O, Rhs>>
 	{
-		using _traits = make_traits<value_type_of<O>, sqlpp::tag::is_expression>;
+		using _traits = make_traits<value_type_of<O>, tag::is_expression>;
 		using _recursive_traits = make_recursive_traits<Rhs>;
 
 		unary_expression_t(Rhs rhs):

include/sqlpp11/expression_fwd.h

@@ -37,53 +37,53 @@ namespace sqlpp
 	{
 		struct less
 		{
-			using _traits = make_traits<::sqlpp::boolean>;
+			using _traits = make_traits<boolean>;
 			static constexpr const char* _name = "<";
 		};
 
 		struct less_equal
 		{
-			using _traits = make_traits<::sqlpp::boolean>;
+			using _traits = make_traits<boolean>;
 			static constexpr const char* _name = "<=";
 		};
 
 		struct equal_to
 		{
-			using _traits = make_traits<::sqlpp::boolean>;
+			using _traits = make_traits<boolean>;
 		};
 
 		struct not_equal_to
 		{
-			using _traits = make_traits<::sqlpp::boolean>;
+			using _traits = make_traits<boolean>;
 		};
 
 		struct greater_equal
 		{
-			using _traits = make_traits<::sqlpp::boolean>;
+			using _traits = make_traits<boolean>;
 			static constexpr const char* _name = ">=";
 		};
 
 		struct greater
 		{
-			using _traits = make_traits<::sqlpp::boolean>;
+			using _traits = make_traits<boolean>;
 			static constexpr const char* _name = ">";
 		};
 
 		struct logical_or
 		{
-			using _traits = make_traits<::sqlpp::boolean>;
+			using _traits = make_traits<boolean>;
 			static constexpr const char* _name = " OR ";
 		};
 
 		struct logical_and
 		{
-			using _traits = make_traits<::sqlpp::boolean>;
+			using _traits = make_traits<boolean>;
 			static constexpr const char* _name = " AND ";
 		};
 
 		struct logical_not
 		{
-			using _traits = make_traits<::sqlpp::boolean>;
+			using _traits = make_traits<boolean>;
 		};
 
 		template<typename ValueType>
@@ -109,13 +109,13 @@ namespace sqlpp
 
 		struct divides
 		{
-			using _traits = make_traits<::sqlpp::floating_point>;
+			using _traits = make_traits<floating_point>;
 			static constexpr const char* _name = "/";
 		};
 
 		struct modulus
 		{
-			using _traits = make_traits<::sqlpp::integral>;
+			using _traits = make_traits<integral>;
 			static constexpr const char* _name = "%";
 		};
 
@@ -208,6 +208,12 @@ namespace sqlpp
 
 	template<typename Lhs, typename ValueType, typename Rhs>
 		using bitwise_or_t = binary_expression_t<Lhs, op::bitwise_or<ValueType>, Rhs>;
+
+	template<typename Expr>
+		using lhs_t = typename Expr::_lhs_t;
+
+	template<typename Expr>
+		using rhs_t = typename Expr::_rhs_t;
 }
 
 #endif

include/sqlpp11/extra_tables.h

@@ -51,22 +51,22 @@ namespace sqlpp
 	template<typename... Tables>
 		struct extra_tables_t
 		{
-			using _traits = make_traits<no_value_t, ::sqlpp::tag::is_extra_tables>;
+			using _traits = make_traits<no_value_t, tag::is_extra_tables>;
 			struct _recursive_traits
 			{
 				using _parameters = std::tuple<>;
-				using _required_tables = ::sqlpp::detail::type_set<>;
-				using _provided_outer_tables = ::sqlpp::detail::type_set<>;
-				using _provided_tables = ::sqlpp::detail::type_set<>;
-				using _extra_tables = ::sqlpp::detail::type_set<Tables...>;
-				using _can_be_null = std::false_type;
+				using _required_tables = detail::type_set<>;
+				using _provided_outer_tables = detail::type_set<>;
+				using _provided_tables = detail::type_set<>;
+				using _extra_tables = detail::type_set<Tables...>;
+				using _tags = detail::type_set<>;
 			};
 
 			// FIXME: extra_tables must not require tables!
 
 			static_assert(sizeof...(Tables), "at least one table or join argument required in extra_tables()");
-			static_assert(not ::sqlpp::detail::has_duplicates<Tables...>::value, "at least one duplicate argument detected in extra_tables()");
-			static_assert(::sqlpp::detail::all_t<is_table_t<Tables>::value...>::value, "at least one argument is not a table or join in extra_tables()");
+			static_assert(not detail::has_duplicates<Tables...>::value, "at least one duplicate argument detected in extra_tables()");
+			static_assert(detail::all_t<is_table_t<Tables>::value...>::value, "at least one argument is not a table or join in extra_tables()");
 
 			// Data
 			using _data_t = extra_tables_data_t<Tables...>;
@@ -106,7 +106,7 @@ namespace sqlpp
 	// NO EXTRA TABLES YET
 	struct no_extra_tables_t
 	{
-		using _traits = make_traits<no_value_t, ::sqlpp::tag::is_noop>;
+		using _traits = make_traits<no_value_t, tag::is_noop>;
 		using _recursive_traits = make_recursive_traits<>;
 
 		// Data
@@ -140,15 +140,15 @@ namespace sqlpp
 			struct _methods_t
 			{
 				template<typename T>
-					using _new_statement_t = typename Policies::template _new_statement_t<no_extra_tables_t, T>;
+					using _new_statement_t = new_statement<Policies, no_extra_tables_t, T>;
 
 				static void _check_consistency() {}
 
 				template<typename... Args>
-					auto extra_tables(Args...)
+					auto extra_tables(Args...) const
 					-> _new_statement_t<extra_tables_t<Args...>>
 					{
-						return { *static_cast<typename Policies::_statement_t*>(this), extra_tables_data_t<Args...>{} };
+						return { static_cast<const derived_statement_t<Policies>&>(*this), extra_tables_data_t<Args...>{} };
 					}
 			};
 	};

include/sqlpp11/floating_point.h

@@ -38,32 +38,39 @@ namespace sqlpp
 	// floating_point value type
 	struct floating_point
 	{
-		using _traits = make_traits<floating_point, ::sqlpp::tag::is_floating_point, ::sqlpp::tag::is_value_type>;
-		using _tag = ::sqlpp::tag::is_floating_point;
+		using _traits = make_traits<floating_point, tag::is_value_type>;
+		using _tag = tag::is_floating_point;
 		using _cpp_value_type = double;
 
-		struct _parameter_t
+		template<typename T>
+			using _is_valid_operand = is_numeric_t<T>;
+	};
+
+	// floating_point parameter type
+	template<>
+		struct parameter_value_t<floating_point>
 		{
 			using _value_type = floating_point;
+			using _cpp_value_type = typename _value_type::_cpp_value_type;
 
-			_parameter_t():
+			parameter_value_t():
 				_value(0),
 				_is_null(true)
 			{}
 
-			_parameter_t(const _cpp_value_type& value):
+			parameter_value_t(const _cpp_value_type& value):
 				_value(value),
 				_is_null(false)
 			{}
 
-			_parameter_t& operator=(const _cpp_value_type& value)
+			parameter_value_t& operator=(const _cpp_value_type& value)
 			{
 				_value = value;
 				_is_null = false;
 				return *this;
 			}
 
-			_parameter_t& operator=(const tvin_t<wrap_operand_t<_cpp_value_type>>& t)
+			parameter_value_t& operator=(const tvin_t<wrap_operand_t<_cpp_value_type>>& t)
 			{
 				if (t._is_trivial())
 				{
@@ -78,7 +85,7 @@ namespace sqlpp
 				return *this;
 			}
 
-			_parameter_t& operator=(const std::nullptr_t&)
+			parameter_value_t& operator=(const std::nullptr_t&)
 			{
 				_value = 0;
 				_is_null = true;
@@ -108,104 +115,103 @@ namespace sqlpp
 			bool _is_null;
 		};
 
-		template<typename T>
-			struct _is_valid_operand
+	// floating_point expression operators
+	template<typename Expr>
+		struct expression_operators<Expr, floating_point>:
+			public basic_expression_operators<Expr, floating_point>
 		{
-				static constexpr bool value = 
-					is_expression_t<T>::value // expressions are OK
-					and is_numeric_t<T>::value // the correct value type is required, of course
-					;
-			};
+			template<typename T>
+				using _is_valid_operand = is_valid_operand<floating_point, T>;
 
-		template<typename Base>
-			struct expression_operators: public basic_expression_operators<Base, is_numeric_t>
-		{
 			template<typename T>
-				plus_t<Base, floating_point, wrap_operand_t<T>> operator +(T t) const
+				plus_t<Expr, floating_point, wrap_operand_t<T>> operator +(T t) const
 				{
 					using rhs = wrap_operand_t<T>;
 					static_assert(_is_valid_operand<rhs>::value, "invalid rhs operand");
 
-					return { *static_cast<const Base*>(this), rhs{t} };
+					return { *static_cast<const Expr*>(this), rhs{t} };
 				}
 
 			template<typename T>
-				minus_t<Base, floating_point, wrap_operand_t<T>> operator -(T t) const
+				minus_t<Expr, floating_point, wrap_operand_t<T>> operator -(T t) const
 				{
 					using rhs = wrap_operand_t<T>;
 					static_assert(_is_valid_operand<rhs>::value, "invalid rhs operand");
 
-					return { *static_cast<const Base*>(this), rhs{t} };
+					return { *static_cast<const Expr*>(this), rhs{t} };
 				}
 
 			template<typename T>
-				multiplies_t<Base, floating_point, wrap_operand_t<T>> operator *(T t) const
+				multiplies_t<Expr, floating_point, wrap_operand_t<T>> operator *(T t) const
 				{
 					using rhs = wrap_operand_t<T>;
 
-					return { *static_cast<const Base*>(this), rhs{t} };
+					return { *static_cast<const Expr*>(this), rhs{t} };
 				}
 
 			template<typename T>
-				divides_t<Base, wrap_operand_t<T>> operator /(T t) const
+				divides_t<Expr, wrap_operand_t<T>> operator /(T t) const
 				{
 					using rhs = wrap_operand_t<T>;
 
-					return { *static_cast<const Base*>(this), rhs{t} };
+					return { *static_cast<const Expr*>(this), rhs{t} };
 				}
 
-			unary_plus_t<floating_point, Base> operator +() const
+			unary_plus_t<floating_point, Expr> operator +() const
 			{
-				return { *static_cast<const Base*>(this) };
+				return { *static_cast<const Expr*>(this) };
 			}
 
-			unary_minus_t<floating_point, Base> operator -() const
+			unary_minus_t<floating_point, Expr> operator -() const
 			{
-				return { *static_cast<const Base*>(this) };
+				return { *static_cast<const Expr*>(this) };
 			}
 		};
 
-		template<typename Base>
-			struct column_operators
+	// floating_point column operators
+	template<typename Column>
+		struct column_operators<Column, floating_point>
 		{
 			template<typename T>
-					auto operator +=(T t) const -> assignment_t<Base, plus_t<Base, floating_point, wrap_operand_t<T>>>
+				using _is_valid_operand = is_valid_operand<floating_point, T>;
+
+			template<typename T>
+				auto operator +=(T t) const -> assignment_t<Column, plus_t<Column, floating_point, wrap_operand_t<T>>>
 				{
 					using rhs = wrap_operand_t<T>;
 					static_assert(_is_valid_operand<rhs>::value, "invalid rhs assignment operand");
 
-						return { *static_cast<const Base*>(this), { *static_cast<const Base*>(this), rhs{t} } };
+					return { *static_cast<const Column*>(this), { *static_cast<const Column*>(this), rhs{t} } };
 				}
 
 			template<typename T>
-					auto operator -=(T t) const -> assignment_t<Base, minus_t<Base, floating_point, wrap_operand_t<T>>>
+				auto operator -=(T t) const -> assignment_t<Column, minus_t<Column, floating_point, wrap_operand_t<T>>>
 				{
 					using rhs = wrap_operand_t<T>;
 					static_assert(_is_valid_operand<rhs>::value, "invalid rhs assignment operand");
 
-						return { *static_cast<const Base*>(this), { *static_cast<const Base*>(this), rhs{t} } };
+					return { *static_cast<const Column*>(this), { *static_cast<const Column*>(this), rhs{t} } };
 				}
 
 			template<typename T>
-					auto operator /=(T t) const -> assignment_t<Base, divides_t<Base, wrap_operand_t<T>>>
+				auto operator /=(T t) const -> assignment_t<Column, divides_t<Column, wrap_operand_t<T>>>
 				{
 					using rhs = wrap_operand_t<T>;
 					static_assert(_is_valid_operand<rhs>::value, "invalid rhs assignment operand");
 
-						return { *static_cast<const Base*>(this), { *static_cast<const Base*>(this), rhs{t} } };
+					return { *static_cast<const Column*>(this), { *static_cast<const Column*>(this), rhs{t} } };
 				}
 
 			template<typename T>
-					auto operator *=(T t) const -> assignment_t<Base, multiplies_t<Base, floating_point, wrap_operand_t<T>>>
+				auto operator *=(T t) const -> assignment_t<Column, multiplies_t<Column, floating_point, wrap_operand_t<T>>>
 				{
 					using rhs = wrap_operand_t<T>;
 					static_assert(_is_valid_operand<rhs>::value, "invalid rhs assignment operand");
 
-						return { *static_cast<const Base*>(this), { *static_cast<const Base*>(this), rhs{t} } };
+					return { *static_cast<const Column*>(this), { *static_cast<const Column*>(this), rhs{t} } };
 				}
 		};
-	};
-
+	// floating_point result field
 	template<typename Db, typename FieldSpec>
 		struct result_field_t<floating_point, Db, FieldSpec>: public result_field_methods_t<result_field_t<floating_point, Db, FieldSpec>>
 		{

include/sqlpp11/from.h

@@ -59,7 +59,7 @@ namespace sqlpp
 	template<typename Database, typename... Tables>
 		struct from_t
 		{
-			using _traits = make_traits<no_value_t, ::sqlpp::tag::is_from>;
+			using _traits = make_traits<no_value_t, tag::is_from>;
 			using _recursive_traits = make_recursive_traits<Tables...>;
 			using _is_dynamic = is_database<Database>;
 
@@ -79,7 +79,7 @@ namespace sqlpp
 							using _known_table_names = detail::transform_set_t<name_of, _known_tables>;
 							static_assert(not detail::is_element_of<typename Table::_name_t, _known_table_names>::value, "Must not use the same table name twice in from()");
 
-							using ok = ::sqlpp::detail::all_t<_is_dynamic::value, is_table_t<Table>::value>;
+							using ok = detail::all_t<_is_dynamic::value, is_table_t<Table>::value>;
 
 							_add_impl(table, ok()); // dispatch to prevent compile messages after the static_assert
 						}
@@ -125,7 +125,7 @@ namespace sqlpp
 
 	struct no_from_t
 	{
-		using _traits = make_traits<no_value_t, ::sqlpp::tag::is_noop>;
+		using _traits = make_traits<no_value_t, tag::is_noop>;
 		using _recursive_traits = make_recursive_traits<>;
 
 		// Data
@@ -161,12 +161,12 @@ namespace sqlpp
 			{
 				using _database_t = typename Policies::_database_t;
 				template<typename T>
-					using _new_statement_t = typename Policies::template _new_statement_t<no_from_t, T>;
+					using _new_statement_t = new_statement<Policies, no_from_t, T>;
 
 				static void _check_consistency() {}
 
 				template<typename... Tables>
-					auto from(Tables... tables)
+					auto from(Tables... tables) const
 					-> _new_statement_t<from_t<void, Tables...>>
 					{
 						static_assert(sizeof...(Tables), "at least one table or join argument required in from()");
@@ -174,7 +174,7 @@ namespace sqlpp
 					}
 
 				template<typename... Tables>
-					auto dynamic_from(Tables... tables)
+					auto dynamic_from(Tables... tables) const
 					-> _new_statement_t<from_t<_database_t, Tables...>>
 					{
 						static_assert(not std::is_same<_database_t, void>::value, "dynamic_from must not be called in a static statement");
@@ -183,10 +183,10 @@ namespace sqlpp
 
 			private:
 				template<typename Database, typename... Tables>
-					auto _from_impl(Tables... tables)
+					auto _from_impl(Tables... tables) const
 					-> _new_statement_t<from_t<Database, Tables...>>
 					{
-						static_assert(::sqlpp::detail::all_t<is_table_t<Tables>::value...>::value, "at least one argument is not a table or join in from()");
+						static_assert(detail::all_t<is_table_t<Tables>::value...>::value, "at least one argument is not a table or join in from()");
 						static_assert(required_tables_of<from_t<Database, Tables...>>::size::value == 0, "at least one table depends on another table");
 
 						static constexpr std::size_t _number_of_tables = detail::sum(provided_tables_of<Tables>::size::value...);
@@ -195,7 +195,7 @@ namespace sqlpp
 						static_assert(_number_of_tables == _unique_tables::size::value, "at least one duplicate table detected in from()");
 						static_assert(_number_of_tables == _unique_table_names::size::value, "at least one duplicate table name detected in from()");
 
-						return { *static_cast<typename Policies::_statement_t*>(this), from_data_t<Database, Tables...>{tables...} };
+						return { static_cast<const derived_statement_t<Policies>&>(*this), from_data_t<Database, Tables...>{tables...} };
 					}
 
 			};

include/sqlpp11/functions.h

@@ -41,8 +41,10 @@
 #include <sqlpp11/max.h>
 #include <sqlpp11/avg.h>
 #include <sqlpp11/sum.h>
-#include <sqlpp11/verbatim_table.h> // Csaba Csoma suggests: unsafe_sql instead of verbatim
+#include <sqlpp11/verbatim.h> // Csaba Csoma suggests: unsafe_sql instead of verbatim
+#include <sqlpp11/verbatim_table.h>
 #include <sqlpp11/value_or_null.h>
+#include <sqlpp11/eval.h>
 
 namespace sqlpp
 {
@@ -53,44 +55,6 @@ namespace sqlpp
 			return { t };
 		}
 
-	template<typename ValueType> // Csaba Csoma suggests: unsafe_sql instead of verbatim
-		struct verbatim_t: public ValueType::template expression_operators<verbatim_t<ValueType>>,
-		public alias_operators<verbatim_t<ValueType>>
-	{
-		using _traits = make_traits<ValueType, ::sqlpp::tag::is_expression>;
-		struct _recursive_traits : public make_recursive_traits<>
-		{
-			using _can_be_null = std::true_type; // since we do not know what's going on inside the verbatim, we assume it can be null
-		};
-
-		verbatim_t(std::string verbatim): _verbatim(verbatim) {}
-		verbatim_t(const verbatim_t&) = default;
-		verbatim_t(verbatim_t&&) = default;
-		verbatim_t& operator=(const verbatim_t&) = default;
-		verbatim_t& operator=(verbatim_t&&) = default;
-		~verbatim_t() = default;
-
-		std::string _verbatim;
-	};
-
-	template<typename Context, typename ValueType>
-		struct serializer_t<Context, verbatim_t<ValueType>>
-		{
-			using T = verbatim_t<ValueType>;
-
-			static Context& _(const T& t, Context& context)
-			{
-				context << t._verbatim;
-				return context;
-			}
-		};
-
-	template<typename ValueType, typename StringType>
-		auto verbatim(StringType s) -> verbatim_t<ValueType>
-		{
-			return { s };
-		}
-
 	template<typename Expression, typename Db>
 		auto flatten(const Expression& exp, Db& db) -> verbatim_t<value_type_of<Expression>>
 		{
@@ -115,7 +79,7 @@ namespace sqlpp
 	template<typename Container>
 		struct value_list_t // to be used in .in() method
 		{
-			using _traits = make_traits<value_type_t<typename Container::value_type>, ::sqlpp::tag::is_expression>;
+			using _traits = make_traits<value_type_t<typename Container::value_type>, tag::is_expression>;
 			using _recursive_traits = make_recursive_traits<>;
 
 			using _container_t = Container;

include/sqlpp11/group_by.h

@@ -59,16 +59,16 @@ namespace sqlpp
 	template<typename Database, typename... Expressions>
 		struct group_by_t
 		{
-			using _traits = make_traits<no_value_t, ::sqlpp::tag::is_group_by>;
+			using _traits = make_traits<no_value_t, tag::is_group_by>;
 			using _recursive_traits = make_recursive_traits<Expressions...>;
 
 			using _is_dynamic = is_database<Database>;
 
 			static_assert(_is_dynamic::value or sizeof...(Expressions), "at least one expression (e.g. a column) required in group_by()");
 
-			static_assert(not ::sqlpp::detail::has_duplicates<Expressions...>::value, "at least one duplicate argument detected in group_by()");
+			static_assert(not detail::has_duplicates<Expressions...>::value, "at least one duplicate argument detected in group_by()");
 
-			static_assert(::sqlpp::detail::all_t<is_expression_t<Expressions>::value...>::value, "at least one argument is not an expression in group_by()");
+			static_assert(detail::all_t<is_expression_t<Expressions>::value...>::value, "at least one argument is not an expression in group_by()");
 
 			// Data
 			using _data_t = group_by_data_t<Database, Expressions...>;
@@ -90,7 +90,7 @@ namespace sqlpp
 							static_assert(is_expression_t<Expression>::value, "invalid expression argument in group_by::add()");
 							static_assert(TableCheckRequired::value or Policies::template _no_unknown_tables<Expression>::value, "expression uses tables unknown to this statement in group_by::add()");
 
-							using ok = ::sqlpp::detail::all_t<_is_dynamic::value, is_expression_t<Expression>::value>;
+							using ok = detail::all_t<_is_dynamic::value, is_expression_t<Expression>::value>;
 
 							_add_impl(expression, ok()); // dispatch to prevent compile messages after the static_assert
 						}
@@ -135,7 +135,7 @@ namespace sqlpp
 	// NO GROUP BY YET
 	struct no_group_by_t
 	{
-		using _traits = make_traits<no_value_t, ::sqlpp::tag::is_noop>;
+		using _traits = make_traits<no_value_t, tag::is_noop>;
 		using _recursive_traits = make_recursive_traits<>;
 
 		// Data
@@ -170,23 +170,23 @@ namespace sqlpp
 			{
 				using _database_t = typename Policies::_database_t;
 				template<typename T>
-					using _new_statement_t = typename Policies::template _new_statement_t<no_group_by_t, T>;
+					using _new_statement_t = new_statement<Policies, no_group_by_t, T>;
 
 				static void _check_consistency() {}
 
 				template<typename... Args>
-					auto group_by(Args... args)
+					auto group_by(Args... args) const
 					-> _new_statement_t<group_by_t<void, Args...>>
 					{
-						return { *static_cast<typename Policies::_statement_t*>(this), group_by_data_t<void, Args...>{args...} };
+						return { static_cast<const derived_statement_t<Policies>&>(*this), group_by_data_t<void, Args...>{args...} };
 					}
 
 				template<typename... Args>
-					auto dynamic_group_by(Args... args)
+					auto dynamic_group_by(Args... args) const
 					-> _new_statement_t<group_by_t<_database_t, Args...>>
 					{
 						static_assert(not std::is_same<_database_t, void>::value, "dynamic_group_by must not be called in a static statement");
-						return { *static_cast<typename Policies::_statement_t*>(this), group_by_data_t<_database_t, Args...>{args...} };
+						return { static_cast<const derived_statement_t<Policies>&>(*this), group_by_data_t<_database_t, Args...>{args...} };
 					}
 			};
 	};

include/sqlpp11/having.h

@@ -58,13 +58,13 @@ namespace sqlpp
 	template<typename Database, typename... Expressions>
 		struct having_t
 		{
-			using _traits = make_traits<no_value_t, ::sqlpp::tag::is_having>;
+			using _traits = make_traits<no_value_t, tag::is_having>;
 			using _recursive_traits = make_recursive_traits<Expressions...>;
 
 			using _is_dynamic = is_database<Database>;
 
 			static_assert(_is_dynamic::value or sizeof...(Expressions), "at least one expression argument required in having()");
-			static_assert(::sqlpp::detail::all_t<is_expression_t<Expressions>::value...>::value, "at least one argument is not an expression in having()");
+			static_assert(detail::all_t<is_expression_t<Expressions>::value...>::value, "at least one argument is not an expression in having()");
 
 			// Data
 			using _data_t = having_data_t<Database, Expressions...>;
@@ -86,7 +86,7 @@ namespace sqlpp
 							static_assert(is_expression_t<Expression>::value, "invalid expression argument in having::add()");
 							static_assert(not TableCheckRequired::value or Policies::template _no_unknown_tables<Expression>::value, "expression uses tables unknown to this statement in having::add()");
 
-							using ok = ::sqlpp::detail::all_t<_is_dynamic::value, is_expression_t<Expression>::value>;
+							using ok = detail::all_t<_is_dynamic::value, is_expression_t<Expression>::value>;
 
 							_add_impl(expression, ok()); // dispatch to prevent compile messages after the static_assert
 						}
@@ -133,7 +133,7 @@ namespace sqlpp
 	// NO HAVING YET
 	struct no_having_t
 	{
-		using _traits = make_traits<no_value_t, ::sqlpp::tag::is_noop>;
+		using _traits = make_traits<no_value_t, tag::is_noop>;
 		using _recursive_traits = make_recursive_traits<>;
 
 		// Data
@@ -168,23 +168,23 @@ namespace sqlpp
 			{
 				using _database_t = typename Policies::_database_t;
 				template<typename T>
-					using _new_statement_t = typename Policies::template _new_statement_t<no_having_t, T>;
+					using _new_statement_t = new_statement<Policies, no_having_t, T>;
 
 				static void _check_consistency() {}
 
 				template<typename... Args>
-					auto having(Args... args)
+					auto having(Args... args) const
 					-> _new_statement_t<having_t<void, Args...>>
 					{
-						return { *static_cast<typename Policies::_statement_t*>(this), having_data_t<void, Args...>{args...} };
+						return { static_cast<const derived_statement_t<Policies>&>(*this), having_data_t<void, Args...>{args...} };
 					}
 
 				template<typename... Args>
-					auto dynamic_having(Args... args)
+					auto dynamic_having(Args... args) const
 					-> _new_statement_t<having_t<_database_t, Args...>>
 					{
 						static_assert(not std::is_same<_database_t, void>::value, "dynamic_having must not be called in a static statement");
-						return { *static_cast<typename Policies::_statement_t*>(this), having_data_t<_database_t, Args...>{args...} };
+						return { static_cast<const derived_statement_t<Policies>&>(*this), having_data_t<_database_t, Args...>{args...} };
 					}
 			};
 	};

include/sqlpp11/in.h

@@ -35,10 +35,11 @@
 namespace sqlpp
 {
 	template<bool NotInverted, typename Operand, typename... Args>
-		struct in_t: public boolean::template expression_operators<in_t<NotInverted, Operand, Args...>>,
+		struct in_t:
+			public expression_operators<in_t<NotInverted, Operand, Args...>, boolean>,
 			public alias_operators<in_t<NotInverted, Operand, Args...>>
 	{
-		using _traits = make_traits<boolean, ::sqlpp::tag::is_expression, ::sqlpp::tag::is_named_expression>;
+		using _traits = make_traits<boolean, tag::is_expression, tag::is_selectable>;
 		using _recursive_traits = make_recursive_traits<Operand, Args...>;
 
 		static constexpr bool _inverted = not NotInverted;
@@ -78,6 +79,10 @@ namespace sqlpp
 			{
 				serialize(t._operand, context);
 				context << (t._inverted ? " NOT IN(" : " IN(");
+				if (sizeof...(Args) == 1)
+					serialize(std::get<0>(t._args), context); // FIXME: this is a bit of a hack until there is a better overall strategy for using braces
+				                                   // see https://github.com/rbock/sqlpp11/issues/18
+				else
 					interpret_tuple(t._args, ',', context);
 				context << ')';
 				return context;

include/sqlpp11/insert.h

@@ -28,6 +28,7 @@
 #define SQLPP_INSERT_H
 
 #include <sqlpp11/statement.h>
+#include <sqlpp11/connection.h>
 #include <sqlpp11/type_traits.h>
 #include <sqlpp11/parameter_list.h>
 #include <sqlpp11/prepared_insert.h>
@@ -48,7 +49,7 @@ namespace sqlpp
 		template<typename Policies>
 			struct _result_methods_t
 			{
-				using _statement_t = typename Policies::_statement_t;
+				using _statement_t = derived_statement_t<Policies>;
 
 				const _statement_t& _get_statement() const
 				{
@@ -111,6 +112,7 @@ namespace sqlpp
 		constexpr auto  dynamic_insert(const Database&)
 		-> decltype(blank_insert_t<Database>())
 		{
+			static_assert(std::is_base_of<connection, Database>::value, "Invalid database parameter");
 			return { blank_insert_t<Database>() };
 		}
 
@@ -118,6 +120,7 @@ namespace sqlpp
 		constexpr auto  dynamic_insert_into(const Database&, Table table)
 		-> decltype(blank_insert_t<Database>().into(table))
 		{
+			static_assert(std::is_base_of<connection, Database>::value, "Invalid database parameter");
 			return { blank_insert_t<Database>().into(table) };
 		}
 }

include/sqlpp11/insert_value.h

@@ -49,7 +49,7 @@ namespace sqlpp
 			{
 				struct type
 				{
-					using _traits = make_traits<no_value_t, ::sqlpp::tag::is_noop>;
+					using _traits = make_traits<no_value_t, tag::is_noop>;
 					using _recursive_traits = make_recursive_traits<>;
 				};
 			};
@@ -62,7 +62,7 @@ namespace sqlpp
 			using _column_t = Column;
 			static constexpr bool _trivial_value_is_null = trivial_value_is_null_t<Column>::value;
 			using _pure_value_t = typename value_type_of<Column>::_cpp_value_type;
-			using _wrapped_value_t = typename wrap_operand<_pure_value_t>::type;
+			using _wrapped_value_t = wrap_operand_t<_pure_value_t>;
 			using _tvin_t = tvin_t<_wrapped_value_t>;
 
 			insert_value_t(rhs_wrap_t<_wrapped_value_t, _trivial_value_is_null> rhs):

include/sqlpp11/insert_value_list.h

@@ -35,6 +35,7 @@
 #include <sqlpp11/insert_value.h>
 #include <sqlpp11/simple_column.h>
 #include <sqlpp11/no_data.h>
+#include <sqlpp11/policy_update.h>
 
 namespace sqlpp
 {
@@ -105,7 +106,7 @@ namespace sqlpp
 			insert_list_data_t(Assignments... assignments):
 				_assignments(assignments...),
 				_columns({assignments._lhs}...),
-				_values({assignments._rhs}...)
+				_values(assignments._rhs...)
 				{}
 
 			insert_list_data_t(const insert_list_data_t&) = default;
@@ -115,8 +116,8 @@ namespace sqlpp
 			~insert_list_data_t() = default;
 
 			std::tuple<Assignments...> _assignments; // FIXME: Need to replace _columns and _values by _assignments (connector-container requires assignments)
-			std::tuple<simple_column_t<typename Assignments::_lhs_t>...> _columns;
-			std::tuple<typename Assignments::_rhs_t...> _values;
+			std::tuple<simple_column_t<lhs_t<Assignments>>...> _columns;
+			std::tuple<rhs_t<Assignments>...> _values;
 			interpretable_list_t<Database> _dynamic_columns;
 			interpretable_list_t<Database> _dynamic_values;
 		};
@@ -124,8 +125,8 @@ namespace sqlpp
 	template<typename Database, typename... Assignments>
 		struct insert_list_t
 		{
-			using _traits = make_traits<no_value_t, ::sqlpp::tag::is_insert_list>;
-			using _recursive_traits = make_recursive_traits<typename Assignments::_lhs_t..., typename Assignments::_rhs_t...>;
+			using _traits = make_traits<no_value_t, tag::is_insert_list>;
+			using _recursive_traits = make_recursive_traits<lhs_t<Assignments>..., rhs_t<Assignments>...>;
 
 			using _is_dynamic = is_database<Database>;
 
@@ -152,12 +153,12 @@ namespace sqlpp
 						{
 							static_assert(_is_dynamic::value, "add must not be called for static from()");
 							static_assert(is_assignment_t<Assignment>::value, "add() arguments require to be assigments");
-							using _assigned_columns = detail::make_type_set_t<typename Assignments::_lhs_t...>;
-							static_assert(not detail::is_element_of<typename Assignment::_lhs_t, _assigned_columns>::value, "Must not assign value to column twice");
-							static_assert(not must_not_insert_t<typename Assignment::_lhs_t>::value, "add() argument must not be used in insert");
+							using _assigned_columns = detail::make_type_set_t<lhs_t<Assignments>...>;
+							static_assert(not detail::is_element_of<lhs_t<Assignment>, _assigned_columns>::value, "Must not assign value to column twice");
+							static_assert(not must_not_insert_t<lhs_t<Assignment>>::value, "add() argument must not be used in insert");
 							static_assert(not TableCheckRequired::value or Policies::template _no_unknown_tables<Assignment>::value, "add() contains a column from a foreign table");
 
-							using ok = ::sqlpp::detail::all_t<
+							using ok = detail::all_t<
 								_is_dynamic::value, 
 								is_assignment_t<Assignment>::value>;
 
@@ -168,7 +169,7 @@ namespace sqlpp
 					template<typename Assignment>
 						void _add_impl(Assignment assignment, const std::true_type&)
 						{
-							_data._dynamic_columns.emplace_back(simple_column_t<typename Assignment::_lhs_t>{assignment._lhs});
+							_data._dynamic_columns.emplace_back(simple_column_t<lhs_t<Assignment>>{assignment._lhs});
 							_data._dynamic_values.emplace_back(assignment._rhs);
 						}
 
@@ -225,7 +226,7 @@ namespace sqlpp
 	template<typename... Columns>
 		struct column_list_t
 		{
-			using _traits = make_traits<no_value_t, ::sqlpp::tag::is_column_list>;
+			using _traits = make_traits<no_value_t, tag::is_column_list>;
 			using _recursive_traits = make_recursive_traits<Columns...>;
 
 			using _value_tuple_t = typename column_list_data_t<Columns...>::_value_tuple_t;
@@ -241,13 +242,13 @@ namespace sqlpp
 					template<typename... Assignments>
 						void add(Assignments... assignments)
 						{
-							static_assert(::sqlpp::detail::all_t<is_assignment_t<Assignments>::value...>::value, "add_values() arguments have to be assignments");
-							using _arg_value_tuple = std::tuple<insert_value_t<typename Assignments::_lhs_t>...>;
+							static_assert(detail::all_t<is_assignment_t<Assignments>::value...>::value, "add_values() arguments have to be assignments");
+							using _arg_value_tuple = std::tuple<insert_value_t<lhs_t<Assignments>>...>;
 							using _args_correct = std::is_same<_arg_value_tuple, _value_tuple_t>;
 							static_assert(_args_correct::value, "add_values() arguments do not match columns() arguments");
 
-							using ok = ::sqlpp::detail::all_t<
-								::sqlpp::detail::all_t<is_assignment_t<Assignments>::value...>::value, 
+							using ok = detail::all_t<
+								detail::all_t<is_assignment_t<Assignments>::value...>::value, 
 								_args_correct::value>;
 
 							_add_impl(ok(), assignments...); // dispatch to prevent compile messages after the static_assert
@@ -257,7 +258,7 @@ namespace sqlpp
 					template<typename... Assignments>
 						void _add_impl(const std::true_type&, Assignments... assignments)
 						{
-							return _data._insert_values.emplace_back(insert_value_t<typename Assignments::_lhs_t>{assignments._rhs}...);
+							return _data._insert_values.emplace_back(insert_value_t<lhs_t<Assignments>>{assignments._rhs}...);
 						}
 
 					template<typename... Assignments>
@@ -294,7 +295,7 @@ namespace sqlpp
 	// NO INSERT COLUMNS/VALUES YET
 	struct no_insert_value_list_t
 	{
-		using _traits = make_traits<no_value_t, ::sqlpp::tag::is_noop>;
+		using _traits = make_traits<no_value_t, tag::is_noop>;
 		using _recursive_traits = make_recursive_traits<>;
 
 		// Data
@@ -329,28 +330,28 @@ namespace sqlpp
 			{
 				using _database_t = typename Policies::_database_t;
 				template<typename T>
-					using _new_statement_t = typename Policies::template _new_statement_t<no_insert_value_list_t, T>;
+					using _new_statement_t = new_statement<Policies, no_insert_value_list_t, T>;
 
 				static void _check_consistency() 
 				{
 					static_assert(wrong_t<_methods_t>::value, "insert values required, e.g. set(...) or default_values()");
 				}
 
-				auto default_values()
+				auto default_values() const
 					-> _new_statement_t<insert_default_values_t>
 					{
-						return { *static_cast<typename Policies::_statement_t*>(this), insert_default_values_data_t{} };
+						return { static_cast<const derived_statement_t<Policies>&>(*this), insert_default_values_data_t{} };
 					}
 
 				template<typename... Columns>
-					auto columns(Columns... columns)
+					auto columns(Columns... columns) const
 					-> _new_statement_t<column_list_t<Columns...>>
 					{
 						static_assert(sizeof...(Columns), "at least one column required in columns()");
-						static_assert(not ::sqlpp::detail::has_duplicates<Columns...>::value, "at least one duplicate argument detected in columns()");
-						static_assert(::sqlpp::detail::all_t<is_column_t<Columns>::value...>::value, "at least one argument is not a column in columns()");
-						static_assert(::sqlpp::detail::none_t<must_not_insert_t<Columns>::value...>::value, "at least one column argument has a must_not_insert tag in its definition");
-						using _column_required_tables = ::sqlpp::detail::make_joined_set_t<required_tables_of<Columns>...>;
+						static_assert(not detail::has_duplicates<Columns...>::value, "at least one duplicate argument detected in columns()");
+						static_assert(detail::all_t<is_column_t<Columns>::value...>::value, "at least one argument is not a column in columns()");
+						static_assert(detail::none_t<must_not_insert_t<Columns>::value...>::value, "at least one column argument has a must_not_insert tag in its definition");
+						using _column_required_tables = detail::make_joined_set_t<required_tables_of<Columns>...>;
 						static_assert(_column_required_tables::size::value == 1, "columns() contains columns from several tables");
 
 						using _table = typename detail::first_arg_t<Columns...>::_table;
@@ -358,43 +359,43 @@ namespace sqlpp
 						using set_columns = detail::make_type_set_t<Columns...>;
 						static_assert(detail::is_subset_of<required_columns, set_columns>::value, "At least one required column is missing in columns()");
 
-						return { *static_cast<typename Policies::_statement_t*>(this), column_list_data_t<Columns...>{columns...} };
+						return { static_cast<const derived_statement_t<Policies>&>(*this), column_list_data_t<Columns...>{columns...} };
 					}
 
 				template<typename... Assignments>
-					auto set(Assignments... assignments)
+					auto set(Assignments... assignments) const
 					-> _new_statement_t<insert_list_t<void, Assignments...>>
 					{
 						static_assert(sizeof...(Assignments), "at least one assignment expression required in set()");
-						static_assert(sqlpp::detail::all_t<is_assignment_t<Assignments>::value...>::value, "at least one argument is not an assignment in set()");
+						static_assert(detail::all_t<is_assignment_t<Assignments>::value...>::value, "at least one argument is not an assignment in set()");
 
-						using _table = typename detail::first_arg_t<Assignments...>::_lhs_t::_table;
+						using _table = typename lhs_t<detail::first_arg_t<Assignments...>>::_table;
 						using required_columns = typename _table::_required_insert_columns;
-						using columns = detail::make_type_set_t<typename Assignments::_lhs_t...>;
+						using columns = detail::make_type_set_t<lhs_t<Assignments>...>;
 						static_assert(detail::is_subset_of<required_columns, columns>::value, "At least one required column is missing in set()");
 						return _set_impl<void>(assignments...);
 					}
 
 				template<typename... Assignments>
-					auto dynamic_set(Assignments... assignments)
+					auto dynamic_set(Assignments... assignments) const
 					-> _new_statement_t<insert_list_t<_database_t, Assignments...>>
 					{
 						static_assert(not std::is_same<_database_t, void>::value, "dynamic_set must not be called in a static statement");
+						static_assert(detail::all_t<is_assignment_t<Assignments>::value...>::value, "at least one argument is not an assignment in set()");
 						return _set_impl<_database_t>(assignments...);
 					}
 			private:
 				template<typename Database, typename... Assignments>
-					auto _set_impl(Assignments... assignments)
+					auto _set_impl(Assignments... assignments) const
 					-> _new_statement_t<insert_list_t<Database, Assignments...>>
 					{
-						static_assert(not ::sqlpp::detail::has_duplicates<Assignments...>::value, "at least one duplicate argument detected in set()");
-						static_assert(sqlpp::detail::all_t<is_assignment_t<Assignments>::value...>::value, "at least one argument is not an assignment in set()");
-						static_assert(sqlpp::detail::none_t<must_not_insert_t<typename Assignments::_lhs_t>::value...>::value, "at least one assignment is prohibited by its column definition in set()");
+						static_assert(not detail::has_duplicates<lhs_t<Assignments>...>::value, "at least one duplicate column detected in set()");
+						static_assert(detail::none_t<must_not_insert_t<lhs_t<Assignments>>::value...>::value, "at least one assignment is prohibited by its column definition in set()");
 
-						using _column_required_tables = ::sqlpp::detail::make_joined_set_t<required_tables_of<typename Assignments::_lhs_t>...>;
+						using _column_required_tables = detail::make_joined_set_t<required_tables_of<lhs_t<Assignments>>...>;
 						static_assert(sizeof...(Assignments) ? (_column_required_tables::size::value == 1) : true, "set() contains assignments for columns from several tables");
 
-						return { *static_cast<typename Policies::_statement_t*>(this), insert_list_data_t<Database, Assignments...>{assignments...} };
+						return { static_cast<const derived_statement_t<Policies>&>(*this), insert_list_data_t<Database, Assignments...>{assignments...} };
 					}
 			};
 	};

include/sqlpp11/integral.h

@@ -40,32 +40,39 @@ namespace sqlpp
 	// integral value type
 	struct integral
 	{
-		using _traits = make_traits<integral, ::sqlpp::tag::is_integral, ::sqlpp::tag::is_value_type>;
-		using _tag = ::sqlpp::tag::is_integral;
+		using _traits = make_traits<integral, tag::is_value_type>;
+		using _tag = tag::is_integral;
 		using _cpp_value_type = int64_t;
 
-		struct _parameter_t
+		template<typename T>
+			using _is_valid_operand = is_numeric_t<T>;
+	};
+
+	// integral parameter value
+	template<>
+	struct parameter_value_t<integral>
 	{
 		using _value_type = integral;
+		using _cpp_value_type = typename _value_type::_cpp_value_type;
 
-			_parameter_t():
+		parameter_value_t():
 			_value(0),
 			_is_null(true)
 		{}
 
-			explicit _parameter_t(const _cpp_value_type& value):
+		explicit parameter_value_t(const _cpp_value_type& value):
 			_value(value),
 			_is_null(false)
 		{}
 
-			_parameter_t& operator=(const _cpp_value_type& value)
+		parameter_value_t& operator=(const _cpp_value_type& value)
 		{
 			_value = value;
 			_is_null = false;
 			return *this;
 		}
 
-			_parameter_t& operator=(const tvin_t<wrap_operand_t<_cpp_value_type>>& t)
+		parameter_value_t& operator=(const tvin_t<wrap_operand_t<_cpp_value_type>>& t)
 		{
 			if (t._is_trivial())
 			{
@@ -109,18 +116,13 @@ namespace sqlpp
 		bool _is_null;
 	};
 
-		template<typename T>
-			struct _is_valid_operand
-			{
-				static constexpr bool value = 
-					is_expression_t<T>::value // expressions are OK
-					and is_numeric_t<T>::value // the correct value type is required, of course
-					;
-			};
-
+	// integral expression operators
 	template<typename Base>
-			struct expression_operators: public basic_expression_operators<Base, is_numeric_t>
+		struct expression_operators<Base, integral>: public basic_expression_operators<Base, integral>
 	{
+		template<typename T>
+			using _is_valid_operand = is_valid_operand<integral, T>;
+
 		template<typename T>
 			plus_t<Base, value_type_t<T>, wrap_operand_t<T>> operator +(T t) const
 			{
@@ -196,16 +198,20 @@ namespace sqlpp
 
 	};
 
+	// integral column operators
 	template<typename Base>
-			struct column_operators
+		struct column_operators<Base, integral>
 		{
+			template<typename T>
+				using _is_valid_operand = is_valid_operand<integral, T>;
+
 			template<typename T>
 				auto operator +=(T t) const -> assignment_t<Base, plus_t<Base, value_type_t<T>, wrap_operand_t<T>>>
 				{
 					using rhs = wrap_operand_t<T>;
 					static_assert(_is_valid_operand<rhs>::value, "invalid rhs assignment operand");
 
-						return { *static_cast<const Base*>(this), { *static_cast<const Base*>(this), rhs{t} } };
+					return { *static_cast<const Base*>(this), {{*static_cast<const Base*>(this), rhs{t}}}};
 				}
 
 			template<typename T>
@@ -214,7 +220,7 @@ namespace sqlpp
 					using rhs = wrap_operand_t<T>;
 					static_assert(_is_valid_operand<rhs>::value, "invalid rhs assignment operand");
 
-						return { *static_cast<const Base*>(this), { *static_cast<const Base*>(this), rhs{t} } };
+					return { *static_cast<const Base*>(this), {{*static_cast<const Base*>(this), rhs{t}}}};
 				}
 
 			template<typename T>
@@ -223,7 +229,7 @@ namespace sqlpp
 					using rhs = wrap_operand_t<T>;
 					static_assert(_is_valid_operand<rhs>::value, "invalid rhs assignment operand");
 
-						return { *static_cast<const Base*>(this), { *static_cast<const Base*>(this), rhs{t} } };
+					return { *static_cast<const Base*>(this), {{*static_cast<const Base*>(this), rhs{t}}}};
 				}
 
 			template<typename T>
@@ -232,12 +238,11 @@ namespace sqlpp
 					using rhs = wrap_operand_t<T>;
 					static_assert(_is_valid_operand<rhs>::value, "invalid rhs assignment operand");
 
-						return { *static_cast<const Base*>(this), { *static_cast<const Base*>(this), rhs{t} } };
+					return { *static_cast<const Base*>(this), {{*static_cast<const Base*>(this), rhs{t}}}};
 				}
 		};
-	};
-
 
+	// integral result field
 	template<typename Db, typename FieldSpec>
 		struct result_field_t<integral, Db, FieldSpec>: public result_field_methods_t<result_field_t<integral, Db, FieldSpec>>
 	{
@@ -308,6 +313,7 @@ namespace sqlpp
 		_cpp_value_type _value;
 	};
 
+	// ostream operator for integral result field
 	template<typename Db, typename FieldSpec>
 		inline std::ostream& operator<<(std::ostream& os, const result_field_t<integral, Db, FieldSpec>& e)
 		{

include/sqlpp11/interpret_tuple.h

@@ -47,7 +47,7 @@ namespace sqlpp
 		}
 
 	template<typename Tuple, typename Separator, typename Context, size_t... Is>
-		auto interpret_tuple_impl(const Tuple& t, const Separator& separator, Context& context, const ::sqlpp::detail::index_sequence<Is...>&)
+		auto interpret_tuple_impl(const Tuple& t, const Separator& separator, Context& context, const detail::index_sequence<Is...>&)
 		-> Context&
 		{
 			// Note: A braced-init-list does guarantee the order of evaluation according to 12.6.1 [class.explicit.init] paragraph 2 and 8.5.4 [dcl.init.list] paragraph 4.
@@ -63,7 +63,7 @@ namespace sqlpp
 		auto interpret_tuple(const Tuple& t, const Separator& separator, Context& context)
 		-> Context&
 		{
-			return interpret_tuple_impl(t, separator, context, ::sqlpp::detail::make_index_sequence<std::tuple_size<Tuple>::value>{});
+			return interpret_tuple_impl(t, separator, context, detail::make_index_sequence<std::tuple_size<Tuple>::value>{});
 		}
 }
 

include/sqlpp11/interpretable.h

@@ -52,16 +52,16 @@ namespace sqlpp
 			interpretable_t& operator=(interpretable_t&&) = default;
 			~interpretable_t() = default;
 
-			sqlpp::serializer_context_t& serialize(sqlpp::serializer_context_t& context) const
+			serializer_context_t& serialize(serializer_context_t& context) const
 			{
 				return _impl->serialize(context);
 			}
 
-			// This method only exists if Db::_serializer_context_t and sqlpp::serializer_context_t are not the same
+			// This method only exists if Db::_serializer_context_t and serializer_context_t are not the same
 			template<typename Context>
 				auto serialize(Context& context) const
 				-> typename std::enable_if<std::is_same<Context, _serializer_context_t>::value 
-				and not std::is_same<Context, sqlpp::serializer_context_t>::value, Context&>::type
+				and not std::is_same<Context, serializer_context_t>::value, Context&>::type
 				{
 					return _impl->db_serialize(context);
 				}
@@ -74,7 +74,7 @@ namespace sqlpp
 		private:
 			struct _impl_base
 			{
-				virtual sqlpp::serializer_context_t& serialize(sqlpp::serializer_context_t& context) const = 0;
+				virtual serializer_context_t& serialize(serializer_context_t& context) const = 0;
 				virtual _serializer_context_t& db_serialize(_serializer_context_t& context) const = 0;
 				virtual _interpreter_context_t& interpret(_interpreter_context_t& context) const = 0;
 			};
@@ -87,9 +87,9 @@ namespace sqlpp
 					_t(t)
 				{}
 
-				sqlpp::serializer_context_t& serialize(sqlpp::serializer_context_t& context) const
+				serializer_context_t& serialize(serializer_context_t& context) const
 				{
-					sqlpp::serialize(_t, context);
+					::sqlpp::serialize(_t, context);
 					return context;
 				}
 

include/sqlpp11/interpretable_list.h

@@ -84,8 +84,8 @@ namespace sqlpp
 						if (not first)
 						{
 							context << separator;
-							first = false;
 						}
+						first = false;
 						serialize(entry, context);
 					}
 					return context;

include/sqlpp11/into.h

@@ -57,7 +57,7 @@ namespace sqlpp
 	template<typename Database, typename Table>
 		struct into_t
 		{
-			using _traits = make_traits<no_value_t, ::sqlpp::tag::is_into>;
+			using _traits = make_traits<no_value_t, tag::is_into>;
 			using _recursive_traits = make_recursive_traits<Table>;
 
 			static_assert(is_table_t<Table>::value, "argument has to be a table");
@@ -103,7 +103,7 @@ namespace sqlpp
 	// NO INTO YET
 	struct no_into_t
 	{
-		using _traits = make_traits<no_value_t, ::sqlpp::tag::is_noop>;
+		using _traits = make_traits<no_value_t, tag::is_noop>;
 		using _recursive_traits = make_recursive_traits<>;
 
 		// Data
@@ -138,7 +138,7 @@ namespace sqlpp
 			{
 				using _database_t = typename Policies::_database_t;
 				template<typename T>
-					using _new_statement_t = typename Policies::template _new_statement_t<no_into_t, T>;
+					using _new_statement_t = new_statement<Policies, no_into_t, T>;
 
 				static void _check_consistency()
 				{
@@ -146,10 +146,10 @@ namespace sqlpp
 				}
 
 				template<typename... Args>
-					auto into(Args... args)
+					auto into(Args... args) const
 					-> _new_statement_t<into_t<void, Args...>>
 					{
-						return { *static_cast<typename Policies::_statement_t*>(this), into_data_t<void, Args...>{args...} };
+						return { static_cast<const derived_statement_t<Policies>&>(*this), into_data_t<void, Args...>{args...} };
 					}
 			};
 	};

include/sqlpp11/is_null.h

@@ -34,19 +34,15 @@
 namespace sqlpp
 {
 	template<bool NotInverted, typename Operand>
-		struct is_null_t: public boolean::template expression_operators<is_null_t<NotInverted, Operand>>,
+		struct is_null_t:
+			public expression_operators<is_null_t<NotInverted, Operand>, boolean>,
 			public alias_operators<is_null_t<NotInverted, Operand>>
 	{
-		using _traits = make_traits<boolean, ::sqlpp::tag::is_expression, ::sqlpp::tag::is_named_expression>;
+		using _traits = make_traits<boolean, tag::is_expression, tag::is_selectable>;
 		using _recursive_traits = make_recursive_traits<Operand>;
 
 		static constexpr bool _inverted = not NotInverted;
 
-		struct _value_type: public boolean
-		{
-			using _is_named_expression = std::true_type;
-		};
-
 		struct _name_t
 		{
 			static constexpr const char* _get_name() { return _inverted ? "IS NOT NULL" : "IS NULL"; }
@@ -71,9 +67,9 @@ namespace sqlpp
 	};
 
 	template<typename Context, bool NotInverted, typename Operand>
-		struct serializer_t<Context, ::sqlpp::is_null_t<NotInverted, Operand>>
+		struct serializer_t<Context, is_null_t<NotInverted, Operand>>
 		{
-			using T = ::sqlpp::is_null_t<NotInverted, Operand>;
+			using T = is_null_t<NotInverted, Operand>;
 
 			static Context& _(const T& t, Context& context)
 			{

include/sqlpp11/join.h

@@ -73,7 +73,7 @@ namespace sqlpp
 				using _provided_outer_tables = typename JoinType::template _provided_outer_tables<Lhs, Rhs>;
 				using _extra_tables = detail::make_joined_set_t<extra_tables_of<Lhs>, extra_tables_of<Rhs>>;
 				using _parameters = detail::make_parameter_tuple_t<parameters_of<Lhs>, parameters_of<Rhs>>;
-				using _can_be_null = std::false_type;
+				using _tags = detail::type_set<>;
 			};
 
 
@@ -82,7 +82,7 @@ namespace sqlpp
 			static_assert(not is_join_t<Rhs>::value, "rhs argument for join must not be a join");
 			static_assert(is_noop<On>::value or is_on_t<On>::value, "invalid on expression in join().on()");
 
-			static_assert(::sqlpp::detail::is_disjunct_from<provided_tables_of<Lhs>, provided_tables_of<Rhs>>::value, "joined tables must not be identical");
+			static_assert(detail::is_disjunct_from<provided_tables_of<Lhs>, provided_tables_of<Rhs>>::value, "joined tables must not be identical");
 
 			static_assert(_recursive_traits::_required_tables::size::value == 0, "joined tables must not depend on other tables");
 
@@ -94,6 +94,8 @@ namespace sqlpp
 				-> set_on_t<on_t<void, Expr...>>
 				{
 					static_assert(is_noop<On>::value, "cannot call on() twice for a single join()");
+					static_assert(detail::all_t<is_expression_t<Expr>::value...>::value, "at least one argument is not an expression in on()");
+
 					return { _lhs, 
 						_rhs, 
 						{std::tuple<Expr...>{expr...}}

include/sqlpp11/like.h

@@ -34,15 +34,13 @@
 namespace sqlpp
 {
 	template<typename Operand, typename Pattern>
-		struct like_t: public boolean::template expression_operators<like_t<Operand, Pattern>>,
+		struct like_t:
+			public expression_operators<like_t<Operand, Pattern>, boolean>,
 			public alias_operators<like_t<Operand, Pattern>>
 	{
-		using _traits = make_traits<boolean, ::sqlpp::tag::is_expression, ::sqlpp::tag::is_named_expression>;
+		using _traits = make_traits<boolean, tag::is_expression, tag::is_selectable>;
 		using _recursive_traits = make_recursive_traits<Operand, Pattern>;
 
-		static_assert(is_text_t<Operand>::value, "Operand for like() has to be a text");
-		static_assert(is_text_t<Pattern>::value, "Pattern for like() has to be a text");
-
 		struct _name_t
 		{
 			static constexpr const char* _get_name() { return "LIKE"; }
@@ -50,6 +48,8 @@ namespace sqlpp
 				struct _member_t
 				{
 					T like;
+					T& operator()() { return like; }
+					const T& operator()() const { return like; }
 				};
 		};
 

include/sqlpp11/limit.h

@@ -54,7 +54,7 @@ namespace sqlpp
 	template<typename Limit>
 		struct limit_t
 		{
-			using _traits = make_traits<no_value_t, ::sqlpp::tag::is_limit>;
+			using _traits = make_traits<no_value_t, tag::is_limit>;
 			using _recursive_traits = make_recursive_traits<Limit>;
 
 			static_assert(is_integral_t<Limit>::value, "limit requires an integral value or integral parameter");
@@ -105,7 +105,7 @@ namespace sqlpp
 			template<typename Limit>
 				dynamic_limit_data_t(Limit value):
 					_initialized(true),
-					_value(typename wrap_operand<Limit>::type(value))
+					_value(wrap_operand_t<Limit>(value))
 			{
 			}
 
@@ -123,7 +123,7 @@ namespace sqlpp
 	template<typename Database>
 		struct dynamic_limit_t
 		{
-			using _traits = make_traits<no_value_t, ::sqlpp::tag::is_limit>;
+			using _traits = make_traits<no_value_t, tag::is_limit>;
 			using _recursive_traits = make_recursive_traits<>;
 
 			// Data
@@ -137,7 +137,7 @@ namespace sqlpp
 						void set(Limit value)
 						{
 							// FIXME: Make sure that Limit does not require external tables? Need to read up on SQL
-							using arg_t = typename wrap_operand<Limit>::type;
+							using arg_t = wrap_operand_t<Limit>;
 							_data._value = arg_t{value};
 							_data._initialized = true;
 						}
@@ -172,7 +172,7 @@ namespace sqlpp
 
 	struct no_limit_t
 	{
-		using _traits = make_traits<no_value_t, ::sqlpp::tag::is_noop>;
+		using _traits = make_traits<no_value_t, tag::is_noop>;
 		using _recursive_traits = make_recursive_traits<>;
 
 		// Data
@@ -207,22 +207,22 @@ namespace sqlpp
 			{
 				using _database_t = typename Policies::_database_t;
 				template<typename T>
-					using _new_statement_t = typename Policies::template _new_statement_t<no_limit_t, T>;
+					using _new_statement_t = new_statement<Policies, no_limit_t, T>;
 
 				static void _check_consistency() {}
 
 				template<typename Arg>
-					auto limit(Arg arg)
-					-> _new_statement_t<limit_t<typename wrap_operand<Arg>::type>>
+					auto limit(Arg arg) const
+					-> _new_statement_t<limit_t<wrap_operand_t<Arg>>>
 					{
-						return { *static_cast<typename Policies::_statement_t*>(this), limit_data_t<typename wrap_operand<Arg>::type>{{arg}} };
+						return { static_cast<const derived_statement_t<Policies>&>(*this), limit_data_t<wrap_operand_t<Arg>>{{arg}} };
 					}
 
-				auto dynamic_limit()
+				auto dynamic_limit() const
 					-> _new_statement_t<dynamic_limit_t<_database_t>>
 					{
 						static_assert(not std::is_same<_database_t, void>::value, "dynamic_limit must not be called in a static statement");
-						return { *static_cast<typename Policies::_statement_t*>(this), dynamic_limit_data_t<_database_t>{} };
+						return { static_cast<const derived_statement_t<Policies>&>(*this), dynamic_limit_data_t<_database_t>{} };
 					}
 			};
 	};

include/sqlpp11/max.h

@@ -32,13 +32,12 @@
 namespace sqlpp
 {
 	template<typename Expr>
-		struct max_t: public value_type_of<Expr>::template expression_operators<max_t<Expr>>,
+		struct max_t:
+			public expression_operators<max_t<Expr>, value_type_of<Expr>>,
 			public alias_operators<max_t<Expr>>
 	{
-		using _traits = make_traits<value_type_of<Expr>, ::sqlpp::tag::is_expression, ::sqlpp::tag::is_named_expression>;
-		using _recursive_traits = make_recursive_traits<Expr>;
-
-		static_assert(is_expression_t<Expr>::value, "max() requires a value expression as argument");
+		using _traits = make_traits<value_type_of<Expr>, tag::is_expression, tag::is_selectable>;
+		using _recursive_traits = make_recursive_traits<Expr, aggregate_function>;
 
 		struct _name_t
 		{
@@ -82,7 +81,7 @@ namespace sqlpp
 	template<typename T>
 		auto max(T t) -> max_t<wrap_operand_t<T>>
 		{
-			static_assert(is_expression_t<wrap_operand_t<T>>::value, "max() requires a value expression as argument");
+			static_assert(is_expression_t<wrap_operand_t<T>>::value, "max() requires an expression as argument");
 			return { t };
 		}
 

include/sqlpp11/min.h

@@ -32,13 +32,12 @@
 namespace sqlpp
 {
 	template<typename Expr>
-		struct min_t: public value_type_of<Expr>::template expression_operators<min_t<Expr>>,
+		struct min_t:
+			public expression_operators<min_t<Expr>, value_type_of<Expr>>,
 			public alias_operators<min_t<Expr>>
 	{
-		using _traits = make_traits<value_type_of<Expr>, ::sqlpp::tag::is_expression, ::sqlpp::tag::is_named_expression>;
-		using _recursive_traits = make_recursive_traits<Expr>;
-
-		static_assert(is_expression_t<Expr>::value, "min() requires a value expression as argument");
+		using _traits = make_traits<value_type_of<Expr>, tag::is_expression, tag::is_selectable>;
+		using _recursive_traits = make_recursive_traits<Expr, aggregate_function>;
 
 		struct _name_t
 		{
@@ -82,7 +81,7 @@ namespace sqlpp
 	template<typename T>
 		auto min(T t) -> min_t<wrap_operand_t<T>>
 		{
-			static_assert(is_expression_t<wrap_operand_t<T>>::value, "min() requires a value expression as argument");
+			static_assert(is_expression_t<wrap_operand_t<T>>::value, "min() requires an expression as argument");
 			return { t };
 		}
 

include/sqlpp11/multi_column.h

@@ -44,7 +44,7 @@ namespace sqlpp
 			using _traits = make_traits<no_value_t>;
 			using _recursive_traits = make_recursive_traits<Columns...>;
 
-			static_assert(detail::all_t<is_named_expression_t<Columns>::value...>::value, "multi_column parameters need to be named expressions");
+			static_assert(detail::all_t<is_selectable_t<Columns>::value...>::value, "multi_column parameters need to be named expressions");
 
 			multi_column_t(std::tuple<Columns...> columns):
 				_columns(columns)
@@ -66,20 +66,16 @@ namespace sqlpp
 					return { *this };
 				}
 
-
-			using _value_type = no_value_t;
-			using _is_multi_column = std::true_type;
-
 			std::tuple<Columns...> _columns;
 		};
 
 	template<typename AliasProvider, typename... Columns>
 		struct multi_column_alias_t
 		{
-			using _traits = make_traits<no_value_t, tag::is_alias, tag::is_multi_column, tag::is_named_expression>;
+			using _traits = make_traits<no_value_t, tag::is_alias, tag::is_multi_column, tag::is_selectable>;
 			using _recursive_traits = make_recursive_traits<Columns...>;
 
-			static_assert(detail::all_t<is_named_expression_t<Columns>::value...>::value, "multi_column parameters need to be named expressions");
+			static_assert(detail::all_t<is_selectable_t<Columns>::value...>::value, "multi_column parameters need to be named expressions");
 
 			using _name_t = typename AliasProvider::_name_t;
 
@@ -101,12 +97,6 @@ namespace sqlpp
 			multi_column_alias_t& operator=(multi_column_alias_t&&) = default;
 			~multi_column_alias_t() = default;
 
-			struct _value_type: public no_value_t
-			{
-				using _is_named_expression = std::true_type;
-			};
-			using _is_multi_column = std::true_type;
-
 			std::tuple<Columns...> _columns;
 		};
 

include/sqlpp11/named_interpretable.h

@@ -50,16 +50,16 @@ namespace sqlpp
 			named_interpretable_t& operator=(named_interpretable_t&&) = default;
 			~named_interpretable_t() = default;
 
-			sqlpp::serializer_context_t& serialize(sqlpp::serializer_context_t& context) const
+			serializer_context_t& serialize(serializer_context_t& context) const
 			{
 				return _impl->serialize(context);
 			}
 
-			// This method only exists if Db::_serializer_context_t and sqlpp::serializer_context_t are not the same
+			// This method only exists if Db::_serializer_context_t and serializer_context_t are not the same
 			template<typename Context>
 				auto serialize(Context& context) const
 				-> typename std::enable_if<std::is_same<Context, _serializer_context_t>::value 
-				and not std::is_same<Context, sqlpp::serializer_context_t>::value, Context&>::type
+				and not std::is_same<Context, serializer_context_t>::value, Context&>::type
 				{
 					return _impl->db_serialize(context);
 				}
@@ -77,7 +77,7 @@ namespace sqlpp
 		private:
 			struct _impl_base
 			{
-				virtual sqlpp::serializer_context_t& serialize(sqlpp::serializer_context_t& context) const = 0;
+				virtual serializer_context_t& serialize(serializer_context_t& context) const = 0;
 				virtual _serializer_context_t& db_serialize(_serializer_context_t& context) const = 0;
 				virtual _interpreter_context_t& interpret(_interpreter_context_t& context) const = 0;
 				virtual std::string _get_name() const = 0;
@@ -91,9 +91,9 @@ namespace sqlpp
 					_t(t)
 				{}
 
-				sqlpp::serializer_context_t& serialize(sqlpp::serializer_context_t& context) const
+				serializer_context_t& serialize(serializer_context_t& context) const
 				{
-					sqlpp::serialize(_t, context);
+					::sqlpp::serialize(_t, context);
 					return context;
 				}
 

include/sqlpp11/no_value.h

@@ -28,28 +28,24 @@
 #define SQLPP_NO_VALUE_H
 
 #include <type_traits>
+#include <sqlpp11/value_type_fwd.h>
 
 namespace sqlpp
 {
 	struct no_value_t
 	{
 		using _tag = void;
-		template<typename T>
-			struct _is_valid_operand
-			{
-				static constexpr bool value = false;
 	};
 
 	template<typename Base>
-			struct expression_operators
+		struct expression_operators<Base, no_value_t>
 		{
 		};
 
 	template<typename Base>
-			struct column_operators
+		struct column_operators<Base, no_value_t>
 		{
 		};
-	};
 
 }
 #endif

include/sqlpp11/noop.h

@@ -35,7 +35,7 @@ namespace sqlpp
 {
 	struct noop 
 	{
-		using _traits = make_traits<no_value_t, ::sqlpp::tag::is_noop>;
+		using _traits = make_traits<no_value_t, tag::is_noop>;
 		using _recursive_traits = make_recursive_traits<>;
 
 		struct _name_t {};

include/sqlpp11/offset.h

@@ -54,7 +54,7 @@ namespace sqlpp
 	template<typename Offset>
 		struct offset_t
 		{
-			using _traits = make_traits<no_value_t, ::sqlpp::tag::is_offset>;
+			using _traits = make_traits<no_value_t, tag::is_offset>;
 			using _recursive_traits = make_recursive_traits<Offset>;
 
 			static_assert(is_integral_t<Offset>::value, "offset requires an integral value or integral parameter");
@@ -105,7 +105,7 @@ namespace sqlpp
 			template<typename Offset>
 				dynamic_offset_data_t(Offset value):
 					_initialized(true),
-					_value(typename wrap_operand<Offset>::type(value))
+					_value(wrap_operand_t<Offset>(value))
 			{
 			}
 
@@ -123,7 +123,7 @@ namespace sqlpp
 	template<typename Database>
 		struct dynamic_offset_t
 		{
-			using _traits = make_traits<no_value_t, ::sqlpp::tag::is_offset>;
+			using _traits = make_traits<no_value_t, tag::is_offset>;
 			using _recursive_traits = make_recursive_traits<>;
 
 			// Data
@@ -137,7 +137,7 @@ namespace sqlpp
 						void set(Offset value)
 						{
 							// FIXME: Make sure that Offset does not require external tables? Need to read up on SQL
-							using arg_t = typename wrap_operand<Offset>::type;
+							using arg_t = wrap_operand_t<Offset>;
 							_data._value = arg_t{value};
 							_data._initialized = true;
 						}
@@ -171,9 +171,9 @@ namespace sqlpp
 						void set_offset(Offset value)
 						{
 							// FIXME: Make sure that Offset does not require external tables? Need to read up on SQL
-							using arg_t = typename wrap_operand<Offset>::type;
-							static_cast<typename Policies::_statement_t*>(this)->_offset()._value = arg_t{value};
-							static_cast<typename Policies::_statement_t*>(this)->_offset()._initialized = true;
+							using arg_t = wrap_operand_t<Offset>;
+							static_cast<derived_statement_t<Policies>*>(this)->_offset()._value = arg_t{value};
+							static_cast<derived_statement_t<Policies>*>(this)->_offset()._initialized = true;
 						}
 				};
 
@@ -183,7 +183,7 @@ namespace sqlpp
 
 	struct no_offset_t
 	{
-		using _traits = make_traits<no_value_t, ::sqlpp::tag::is_noop>;
+		using _traits = make_traits<no_value_t, tag::is_noop>;
 		using _recursive_traits = make_recursive_traits<>;
 
 		// Data
@@ -218,22 +218,22 @@ namespace sqlpp
 			{
 				using _database_t = typename Policies::_database_t;
 				template<typename T>
-					using _new_statement_t = typename Policies::template _new_statement_t<no_offset_t, T>;
+					using _new_statement_t = new_statement<Policies, no_offset_t, T>;
 
 				static void _check_consistency() {}
 
 				template<typename Arg>
-					auto offset(Arg arg)
-					-> _new_statement_t<offset_t<typename wrap_operand<Arg>::type>>
+					auto offset(Arg arg) const
+					-> _new_statement_t<offset_t<wrap_operand_t<Arg>>>
 					{
-						return { *static_cast<typename Policies::_statement_t*>(this), offset_data_t<typename wrap_operand<Arg>::type>{{arg}} };
+						return { static_cast<const derived_statement_t<Policies>&>(*this), offset_data_t<wrap_operand_t<Arg>>{{arg}} };
 					}
 
-				auto dynamic_offset()
+				auto dynamic_offset() const
 					-> _new_statement_t<dynamic_offset_t<_database_t>>
 					{
 						static_assert(not std::is_same<_database_t, void>::value, "dynamic_offset must not be called in a static statement");
-						return { *static_cast<typename Policies::_statement_t*>(this), dynamic_offset_data_t<_database_t>{} };
+						return { static_cast<const derived_statement_t<Policies>&>(*this), dynamic_offset_data_t<_database_t>{} };
 					}
 			};
 	};

include/sqlpp11/on.h

@@ -43,7 +43,6 @@ namespace sqlpp
 			using _is_dynamic = is_database<Database>;
 
 			static_assert(_is_dynamic::value or sizeof...(Expr), "at least one expression argument required in on()");
-			static_assert(detail::all_t<is_expression_t<Expr>::value...>::value, "at least one argument is not an expression in on()");
 
 			template<typename E>
 				void add(E expr)

include/sqlpp11/order_by.h

@@ -59,16 +59,16 @@ namespace sqlpp
 	template<typename Database, typename... Expressions>
 		struct order_by_t
 		{
-			using _traits = make_traits<no_value_t, ::sqlpp::tag::is_order_by>;
+			using _traits = make_traits<no_value_t, tag::is_order_by>;
 			using _recursive_traits = make_recursive_traits<Expressions...>;
 
 			using _is_dynamic = is_database<Database>;
 
 			static_assert(_is_dynamic::value or sizeof...(Expressions), "at least one expression (e.g. a column) required in order_by()");
 
-			static_assert(not ::sqlpp::detail::has_duplicates<Expressions...>::value, "at least one duplicate argument detected in order_by()");
+			static_assert(not detail::has_duplicates<Expressions...>::value, "at least one duplicate argument detected in order_by()");
 
-			static_assert(::sqlpp::detail::all_t<is_expression_t<Expressions>::value...>::value, "at least one argument is not an expression in order_by()");
+			static_assert(detail::all_t<is_expression_t<Expressions>::value...>::value, "at least one argument is not an expression in order_by()");
 
 			// Data
 			using _data_t = order_by_data_t<Database, Expressions...>;
@@ -90,7 +90,7 @@ namespace sqlpp
 							static_assert(is_expression_t<Expression>::value, "invalid expression argument in order_by::add()");
 							static_assert(TableCheckRequired::value or Policies::template _no_unknown_tables<Expression>::value, "expression uses tables unknown to this statement in order_by::add()");
 
-							using ok = ::sqlpp::detail::all_t<_is_dynamic::value, is_expression_t<Expression>::value>;
+							using ok = detail::all_t<_is_dynamic::value, is_expression_t<Expression>::value>;
 
 							_add_impl(expression, ok()); // dispatch to prevent compile messages after the static_assert
 						}
@@ -135,7 +135,7 @@ namespace sqlpp
 	// NO ORDER BY YET
 	struct no_order_by_t
 	{
-		using _traits = make_traits<no_value_t, ::sqlpp::tag::is_noop>;
+		using _traits = make_traits<no_value_t, tag::is_noop>;
 		using _recursive_traits = make_recursive_traits<>;
 
 		// Data
@@ -170,23 +170,23 @@ namespace sqlpp
 			{
 				using _database_t = typename Policies::_database_t;
 				template<typename T>
-					using _new_statement_t = typename Policies::template _new_statement_t<no_order_by_t, T>;
+					using _new_statement_t = new_statement<Policies, no_order_by_t, T>;
 
 				static void _check_consistency() {}
 
 				template<typename... Args>
-					auto order_by(Args... args)
+					auto order_by(Args... args) const
 					-> _new_statement_t<order_by_t<void, Args...>>
 					{
-						return { *static_cast<typename Policies::_statement_t*>(this), order_by_data_t<void, Args...>{args...} };
+						return { static_cast<const derived_statement_t<Policies>&>(*this), order_by_data_t<void, Args...>{args...} };
 					}
 
 				template<typename... Args>
-					auto dynamic_order_by(Args... args)
+					auto dynamic_order_by(Args... args) const
 					-> _new_statement_t<order_by_t<_database_t, Args...>>
 					{
 						static_assert(not std::is_same<_database_t, void>::value, "dynamic_order_by must not be called in a static statement");
-						return { *static_cast<typename Policies::_statement_t*>(this), order_by_data_t<_database_t, Args...>{args...} };
+						return { static_cast<const derived_statement_t<Policies>&>(*this), order_by_data_t<_database_t, Args...>{args...} };
 					}
 			};
 	};

include/sqlpp11/parameter.h

@@ -34,7 +34,8 @@
 namespace sqlpp
 {
 	template<typename ValueType, typename NameType>
-		struct parameter_t: public ValueType::template expression_operators<parameter_t<ValueType, NameType>>
+		struct parameter_t:
+			public expression_operators<parameter_t<ValueType, NameType>, ValueType>
 	{
 		using _traits = make_traits<ValueType, tag::is_parameter, tag::is_expression>;
 		struct _recursive_traits
@@ -44,10 +45,10 @@ namespace sqlpp
 			using _provided_outer_tables = detail::type_set<>;
 			using _required_tables = detail::type_set<>;
 			using _extra_tables = detail::type_set<>;
-			using _can_be_null = std::true_type;
+			using _tags = detail::type_set<tag::can_be_null>;
 		};
 
-		using _instance_t = typename NameType::_name_t::template _member_t<typename ValueType::_parameter_t>;
+		using _instance_t = member_t<NameType, parameter_value_t<ValueType>>;
 
 		parameter_t()
 		{}
@@ -75,7 +76,7 @@ namespace sqlpp
 		auto parameter(const NamedExpr&)
 		-> parameter_t<value_type_of<NamedExpr>, NamedExpr>
 		{
-			static_assert(is_named_expression_t<NamedExpr>::value, "not a named expression");
+			static_assert(is_selectable_t<NamedExpr>::value, "not a named expression");
 			return {};
 		}
 

include/sqlpp11/parameter_list.h

@@ -52,12 +52,12 @@ namespace sqlpp
 			template<typename Target>
 				void _bind(Target& target) const
 				{
-					_bind_impl(target, ::sqlpp::detail::make_index_sequence<size::value>{});
+					_bind_impl(target, detail::make_index_sequence<size::value>{});
 				}
 
 		private:
 			template<typename Target, size_t... Is>
-				void _bind_impl(Target& target, const ::sqlpp::detail::index_sequence<Is...>&) const
+				void _bind_impl(Target& target, const detail::index_sequence<Is...>&) const
 				{
 					using swallow = int[];  // see interpret_tuple.h
 					(void) swallow{(static_cast<typename std::tuple_element<Is, const _member_tuple_t>::type&>(*this)()._bind(target, Is), 0)...};

include/sqlpp11/policy_update.h

@@ -50,6 +50,8 @@ namespace sqlpp
 	template<typename Original, typename Needle, typename Replacement>
 		using update_policies_t = typename update_policies_impl<Original, Needle, Replacement>::type;
 
+	template<typename Policies, typename Needle, typename Replacement>
+		using new_statement = typename Policies::template _new_statement_t<Needle, Replacement>;
 
 }
 

include/sqlpp11/remove.h

@@ -28,6 +28,7 @@
 #define SQLPP_REMOVE_H
 
 #include <sqlpp11/statement.h>
+#include <sqlpp11/connection.h>
 #include <sqlpp11/type_traits.h>
 #include <sqlpp11/parameter_list.h>
 #include <sqlpp11/prepared_remove.h>
@@ -48,7 +49,7 @@ namespace sqlpp
 		template<typename Policies>
 			struct _result_methods_t
 			{
-				using _statement_t = typename Policies::_statement_t;
+				using _statement_t = derived_statement_t<Policies>;
 
 				const _statement_t& _get_statement() const
 				{
@@ -115,6 +116,7 @@ namespace sqlpp
 		auto  dynamic_remove(const Database&)
 		-> decltype(blank_remove_t<Database>())
 		{
+			static_assert(std::is_base_of<connection, Database>::value, "Invalid database parameter");
 			return { blank_remove_t<Database>() };
 		}
 
@@ -122,6 +124,7 @@ namespace sqlpp
 		auto  dynamic_remove_from(const Database&, Table table)
 		-> decltype(blank_remove_t<Database>().from(table))
 		{
+			static_assert(std::is_base_of<connection, Database>::value, "Invalid database parameter");
 			return { blank_remove_t<Database>().from(table) };
 		}
 }

include/sqlpp11/result_field.h

@@ -32,7 +32,7 @@
 
 namespace sqlpp
 {
-	template<typename ValueType, typename Db, typename Field>
+	template<typename ValueType, typename Db, typename FieldSpec>
 		struct result_field_t
 		{
 			static_assert(wrong_t<result_field_t>::value, "Missing specialization for result_field_t");

include/sqlpp11/result_field_methods.h

@@ -88,7 +88,9 @@ namespace sqlpp
 				using _provided_outer_tables = detail::type_set<>;
 				using _required_tables = detail::type_set<>;
 				using _extra_tables = detail::type_set<>;
-				using _can_be_null = column_spec_can_be_null_t<_field_spec_t>;
+				using _tags = typename std::conditional<column_spec_can_be_null_t<_field_spec_t>::value,
+										detail::type_set<tag::can_be_null>,
+										detail::type_set<>>::type;
 			};
 
 		};

include/sqlpp11/result_row.h

@@ -41,9 +41,9 @@ namespace sqlpp
 
 		template<typename Db, std::size_t index, typename FieldSpec>
 			struct result_field:
-				public FieldSpec::_name_t::template _member_t<result_field_t<value_type_of<FieldSpec>, Db, FieldSpec>>
+				public member_t<FieldSpec, result_field_t<value_type_of<FieldSpec>, Db, FieldSpec>>
 		{
-			using _field = typename FieldSpec::_name_t::template _member_t<result_field_t<value_type_of<FieldSpec>, Db, FieldSpec>>;
+			using _field = member_t<FieldSpec, result_field_t<value_type_of<FieldSpec>, Db, FieldSpec>>;
 
 			result_field() = default;
 
@@ -66,9 +66,9 @@ namespace sqlpp
 
 		template<std::size_t index, typename AliasProvider, typename Db, typename... FieldSpecs>
 			struct result_field<Db, index, multi_field_spec_t<AliasProvider, std::tuple<FieldSpecs...>>>: 
-			public AliasProvider::_name_t::template _member_t<result_row_impl<Db, detail::make_field_index_sequence<index, FieldSpecs...>, FieldSpecs...>>
+			public member_t<AliasProvider, result_row_impl<Db, detail::make_field_index_sequence<index, FieldSpecs...>, FieldSpecs...>>
 			{
-				using _multi_field = typename AliasProvider::_name_t::template _member_t<result_row_impl<Db, detail::make_field_index_sequence<index, FieldSpecs...>, FieldSpecs...>>;
+				using _multi_field = member_t<AliasProvider, result_row_impl<Db, detail::make_field_index_sequence<index, FieldSpecs...>, FieldSpecs...>>;
 
 				result_field() = default;
 

include/sqlpp11/select.h

@@ -30,6 +30,7 @@
 #include <sqlpp11/statement.h>
 
 #include <sqlpp11/noop.h>
+#include <sqlpp11/connection.h>
 #include <sqlpp11/select_flag_list.h>
 #include <sqlpp11/select_column_list.h>
 #include <sqlpp11/from.h>
@@ -94,6 +95,7 @@ namespace sqlpp
 	template<typename Database>
 		blank_select_t<Database> dynamic_select(const Database&)
 		{
+			static_assert(std::is_base_of<connection, Database>::value, "Invalid database parameter");
 			return { };
 		}
 
@@ -101,6 +103,7 @@ namespace sqlpp
 		auto dynamic_select(const Database&, Columns... columns)
 		-> decltype(blank_select_t<Database>().columns(columns...))
 		{
+			static_assert(std::is_base_of<connection, Database>::value, "Invalid database parameter");
 			return blank_select_t<Database>().columns(columns...);
 		}
 

include/sqlpp11/select_column_list.h

@@ -54,7 +54,7 @@ namespace sqlpp
 		template<typename Column>
 			struct select_traits<Column>
 			{
-				using _traits = make_traits<value_type_of<Column>, tag::is_select_column_list, tag::is_return_value, tag::is_expression, tag::is_named_expression>;
+				using _traits = make_traits<value_type_of<Column>, tag::is_select_column_list, tag::is_return_value, tag::is_expression, tag::is_selectable>;
 				using _name_t = typename Column::_name_t;
 			};
 	}
@@ -152,17 +152,17 @@ namespace sqlpp
 	template<typename Database, typename... Columns>
 		struct select_column_list_t
 		{
-			using _traits = typename ::sqlpp::detail::select_traits<Columns...>::_traits;
+			using _traits = typename detail::select_traits<Columns...>::_traits;
 			using _recursive_traits = make_recursive_traits<Columns...>;
 
-			using _name_t = typename ::sqlpp::detail::select_traits<Columns...>::_name_t;
+			using _name_t = typename detail::select_traits<Columns...>::_name_t;
 
 			using _is_dynamic = is_database<Database>;
 
 			static_assert(_is_dynamic::value or sizeof...(Columns), "at least one select expression required");
-			static_assert(not ::sqlpp::detail::has_duplicates<Columns...>::value, "at least one duplicate argument detected");
-			static_assert(::sqlpp::detail::all_t<(is_named_expression_t<Columns>::value or is_multi_column_t<Columns>::value)...>::value, "at least one argument is not a named expression");
-			static_assert(not ::sqlpp::detail::has_duplicates<typename Columns::_name_t...>::value, "at least one duplicate name detected");
+			static_assert(not detail::has_duplicates<Columns...>::value, "at least one duplicate argument detected");
+			static_assert(detail::all_t<(is_selectable_t<Columns>::value or is_multi_column_t<Columns>::value)...>::value, "at least one argument is not a named expression");
+			static_assert(not detail::has_duplicates<typename Columns::_name_t...>::value, "at least one duplicate name detected");
 
 			struct _column_type {};
 
@@ -183,14 +183,14 @@ namespace sqlpp
 						void add(NamedExpression namedExpression)
 						{
 							static_assert(_is_dynamic::value, "selected_columns::add() can only be called for dynamic_column");
-							static_assert(is_named_expression_t<NamedExpression>::value, "invalid named expression argument in selected_columns::add()");
+							static_assert(is_selectable_t<NamedExpression>::value, "invalid named expression argument in selected_columns::add()");
 							static_assert(TableCheckRequired::value or Policies::template _no_unknown_tables<NamedExpression>::value, "named expression uses tables unknown to this statement in selected_columns::add()");
-							using column_names = ::sqlpp::detail::make_type_set_t<typename Columns::_name_t...>;
-							static_assert(not ::sqlpp::detail::is_element_of<typename NamedExpression::_name_t, column_names>::value, "a column of this name is present in the select already");
+							using column_names = detail::make_type_set_t<typename Columns::_name_t...>;
+							static_assert(not detail::is_element_of<typename NamedExpression::_name_t, column_names>::value, "a column of this name is present in the select already");
 
-							using ok = ::sqlpp::detail::all_t<
+							using ok = detail::all_t<
 								_is_dynamic::value, 
-								is_named_expression_t<NamedExpression>::value
+								is_selectable_t<NamedExpression>::value
 									>;
 
 							_add_impl(namedExpression, ok()); // dispatch to prevent compile messages after the static_assert
@@ -238,7 +238,7 @@ namespace sqlpp
 			template<typename Policies>
 				struct _result_methods_t
 				{
-					using _statement_t = typename Policies::_statement_t;
+					using _statement_t = derived_statement_t<Policies>;
 
 					const _statement_t& _get_statement() const
 					{
@@ -278,7 +278,7 @@ namespace sqlpp
 						_alias_t<AliasProvider> as(const AliasProvider& aliasProvider) const
 						{
 							static_assert(Policies::_can_be_used_as_table::value, "statement cannot be used as table, e.g. due to missing tables");
-							static_assert(::sqlpp::detail::none_t<is_multi_column_t<Columns>::value...>::value, "cannot use multi-columns in sub selects");
+							static_assert(detail::none_t<is_multi_column_t<Columns>::value...>::value, "cannot use multi-columns in sub selects");
 							return _table_t<AliasProvider>(_get_statement()).as(aliasProvider);
 						}
 
@@ -310,7 +310,7 @@ namespace sqlpp
 						{
 							_statement_t::_check_consistency();
 
-							return {{}, get_dynamic_names(), db.prepare_select(_get_statement())};
+							return {make_parameter_list_t<_statement_t>{}, get_dynamic_names(), db.prepare_select(_get_statement())};
 						}
 				};
 
@@ -326,7 +326,7 @@ namespace sqlpp
 
 	struct no_select_column_list_t
 	{
-		using _traits = make_traits<no_value_t, ::sqlpp::tag::is_noop, ::sqlpp::tag::is_missing>;
+		using _traits = make_traits<no_value_t, tag::is_noop, tag::is_missing>;
 		using _recursive_traits = make_recursive_traits<>;
 
 		struct _name_t {};
@@ -364,23 +364,23 @@ namespace sqlpp
 			{
 				using _database_t = typename Policies::_database_t;
 				template<typename T>
-					using _new_statement_t = typename Policies::template _new_statement_t<no_select_column_list_t, T>;
+					using _new_statement_t = new_statement<Policies, no_select_column_list_t, T>;
 
 				static void _check_consistency() {}
 
 				template<typename... Args>
-					auto columns(Args... args)
-					-> _new_statement_t<::sqlpp::detail::make_select_column_list_t<void, Args...>>
+					auto columns(Args... args) const
+					-> _new_statement_t<detail::make_select_column_list_t<void, Args...>>
 					{
-						return { *static_cast<typename Policies::_statement_t*>(this), typename ::sqlpp::detail::make_select_column_list_t<void, Args...>::_data_t{std::tuple_cat(::sqlpp::detail::as_tuple<Args>::_(args)...)} };
+						return { static_cast<const derived_statement_t<Policies>&>(*this), typename detail::make_select_column_list_t<void, Args...>::_data_t{std::tuple_cat(detail::as_tuple<Args>::_(args)...)} };
 					}
 
 				template<typename... Args>
-					auto dynamic_columns(Args... args)
-					-> _new_statement_t<::sqlpp::detail::make_select_column_list_t<_database_t, Args...>>
+					auto dynamic_columns(Args... args) const
+					-> _new_statement_t<detail::make_select_column_list_t<_database_t, Args...>>
 					{
 						static_assert(not std::is_same<_database_t, void>::value, "dynamic_columns must not be called in a static statement");
-						return { *static_cast<typename Policies::_statement_t*>(this), typename ::sqlpp::detail::make_select_column_list_t<_database_t, Args...>::_data_t{std::tuple_cat(::sqlpp::detail::as_tuple<Args>::_(args)...)} };
+						return { static_cast<const derived_statement_t<Policies>&>(*this), typename detail::make_select_column_list_t<_database_t, Args...>::_data_t{std::tuple_cat(detail::as_tuple<Args>::_(args)...)} };
 					}
 			};
 	};

include/sqlpp11/select_flag_list.h

@@ -59,14 +59,14 @@ namespace sqlpp
 	template<typename Database, typename... Flags>
 		struct select_flag_list_t
 		{
-			using _traits = make_traits<no_value_t, ::sqlpp::tag::is_select_flag_list>;
+			using _traits = make_traits<no_value_t, tag::is_select_flag_list>;
 			using _recursive_traits = make_recursive_traits<Flags...>;
 
 			using _is_dynamic = is_database<Database>;
 
-			static_assert(not ::sqlpp::detail::has_duplicates<Flags...>::value, "at least one duplicate argument detected in select flag list");
+			static_assert(not detail::has_duplicates<Flags...>::value, "at least one duplicate argument detected in select flag list");
 
-			static_assert(::sqlpp::detail::all_t<is_select_flag_t<Flags>::value...>::value, "at least one argument is not a select flag in select flag list");
+			static_assert(detail::all_t<is_select_flag_t<Flags>::value...>::value, "at least one argument is not a select flag in select flag list");
 
 			// Data
 			using _data_t = select_flag_list_data_t<Database, Flags...>;
@@ -88,7 +88,7 @@ namespace sqlpp
 							static_assert(is_select_flag_t<Flag>::value, "invalid select flag argument in select_flags::add()");
 							static_assert(TableCheckRequired::value or Policies::template _no_unknown_tables<Flag>::value, "flag uses tables unknown to this statement in select_flags::add()");
 
-							using ok = ::sqlpp::detail::all_t<_is_dynamic::value, is_select_flag_t<Flag>::value>;
+							using ok = detail::all_t<_is_dynamic::value, is_select_flag_t<Flag>::value>;
 
 							_add_impl(flag, ok()); // dispatch to prevent compile messages after the static_assert
 						}
@@ -134,7 +134,7 @@ namespace sqlpp
 
 	struct no_select_flag_list_t
 	{
-		using _traits = make_traits<no_value_t, ::sqlpp::tag::is_noop>;
+		using _traits = make_traits<no_value_t, tag::is_noop>;
 		using _recursive_traits = make_recursive_traits<>;
 
 		// Data
@@ -169,23 +169,23 @@ namespace sqlpp
 			{
 				using _database_t = typename Policies::_database_t;
 				template<typename T>
-					using _new_statement_t = typename Policies::template _new_statement_t<no_select_flag_list_t, T>;
+					using _new_statement_t = new_statement<Policies, no_select_flag_list_t, T>;
 
 				static void _check_consistency() {}
 
 				template<typename... Args>
-					auto flags(Args... args)
+					auto flags(Args... args) const
 					-> _new_statement_t<select_flag_list_t<void, Args...>>
 					{
-						return { *static_cast<typename Policies::_statement_t*>(this), select_flag_list_data_t<void, Args...>{args...} };
+						return { static_cast<const derived_statement_t<Policies>&>(*this), select_flag_list_data_t<void, Args...>{args...} };
 					}
 
 				template<typename... Args>
-					auto dynamic_flags(Args... args)
+					auto dynamic_flags(Args... args) const
 					-> _new_statement_t<select_flag_list_t<_database_t, Args...>>
 					{
 						static_assert(not std::is_same<_database_t, void>::value, "dynamic_flags must not be called in a static statement");
-						return { *static_cast<typename Policies::_statement_t*>(this), select_flag_list_data_t<_database_t, Args...>{args...} };
+						return { static_cast<const derived_statement_t<Policies>&>(*this), select_flag_list_data_t<_database_t, Args...>{args...} };
 					}
 			};
 	};

include/sqlpp11/select_pseudo_table.h

@@ -51,7 +51,7 @@ namespace sqlpp
 		typename Select,
 						 typename... NamedExpr
 							 >
-							 struct select_pseudo_table_t: public sqlpp::table_t<select_pseudo_table_t<
+							 struct select_pseudo_table_t: public table_t<select_pseudo_table_t<
 																						 Select,
 																						 NamedExpr...>, select_column_spec_t<Select, NamedExpr>...>
 	{

include/sqlpp11/simple_column.h

@@ -37,7 +37,7 @@ namespace sqlpp
 		{
 			Column _column;
 
-			using _traits = make_traits<no_value_t, ::sqlpp::tag::is_noop>;
+			using _traits = make_traits<no_value_t, tag::is_noop>;
 			using _recursive_traits = make_recursive_traits<>;
 		};
 

include/sqlpp11/single_table.h

@@ -57,7 +57,7 @@ namespace sqlpp
 	template<typename Database, typename Table>
 		struct single_table_t
 		{
-			using _traits = make_traits<no_value_t, ::sqlpp::tag::is_single_table>;
+			using _traits = make_traits<no_value_t, tag::is_single_table>;
 			using _recursive_traits = make_recursive_traits<Table>;
 
 			static_assert(is_table_t<Table>::value, "argument has to be a table");
@@ -103,7 +103,7 @@ namespace sqlpp
 	// NO INTO YET
 	struct no_single_table_t
 	{
-		using _traits = make_traits<no_value_t, ::sqlpp::tag::is_noop>;
+		using _traits = make_traits<no_value_t, tag::is_noop>;
 		using _recursive_traits = make_recursive_traits<>;
 
 		// Data
@@ -138,15 +138,15 @@ namespace sqlpp
 			{
 				using _database_t = typename Policies::_database_t;
 				template<typename T>
-					using _new_statement_t = typename Policies::template _new_statement_t<no_single_table_t, T>;
+					using _new_statement_t = new_statement<Policies, no_single_table_t, T>;
 
 				static void _check_consistency() {}
 
 				template<typename... Args>
-					auto from(Args... args)
+					auto from(Args... args) const
 					-> _new_statement_t<single_table_t<void, Args...>>
 					{
-						return { *static_cast<typename Policies::_statement_t*>(this), single_table_data_t<void, Args...>{args...} };
+						return { static_cast<const derived_statement_t<Policies>&>(*this), single_table_data_t<void, Args...>{args...} };
 					}
 			};
 	};

include/sqlpp11/some.h

@@ -35,7 +35,7 @@ namespace sqlpp
 	template<typename Select>
 		struct some_t
 		{
-			using _traits = make_traits<value_type_of<Select>, ::sqlpp::tag::is_multi_expression>;
+			using _traits = make_traits<value_type_of<Select>, tag::is_multi_expression>;
 			using _recursive_traits = make_recursive_traits<Select>;
 
 			struct _name_t

include/sqlpp11/sort_order.h

@@ -41,7 +41,7 @@ namespace sqlpp
 	template<typename Expression, sort_type SortType>
 		struct sort_order_t
 		{
-			using _traits = make_traits<no_value_t,  tag::is_sort_order, sqlpp::tag::is_expression>;
+			using _traits = make_traits<no_value_t,  tag::is_sort_order, tag::is_expression>;
 			using _recursive_traits = make_recursive_traits<Expression>;
 
 			Expression _expression;

include/sqlpp11/statement.h

@@ -98,6 +98,13 @@ namespace sqlpp
 					no_value_t // if a required statement part is missing (e.g. columns in a select), then the statement cannot be used as a value
 						>::type;
 
+				using _can_be_null = detail::any_t<
+					can_be_null_t<_result_type_provider>::value, 
+					detail::make_intersect_set_t<
+						required_tables_of<_result_type_provider>, 
+						_all_provided_outer_tables
+						>::size::value != 0>;
+
 				using _traits = make_traits<_value_type, tag_if<tag::is_expression, not std::is_same<_value_type, no_value_t>::value>>;
 
 				struct _recursive_traits
@@ -107,12 +114,9 @@ namespace sqlpp
 					using _provided_outer_tables = detail::type_set<>;
 					using _extra_tables = detail::type_set<>;
 					using _parameters = detail::make_parameter_tuple_t<parameters_of<Policies>...>;
-					using _can_be_null = detail::any_t<
-									can_be_null_t<_result_type_provider>::value, 
-									::sqlpp::detail::make_intersect_set_t<
-									  required_tables_of<_result_type_provider>, 
-								    provided_outer_tables_of<statement_policies_t>
-								  >::size::value != 0>;
+					using _tags = typename std::conditional<_can_be_null::value,
+											detail::type_set<tag::can_be_null>,
+											detail::type_set<>>::type;
 				};
 			};
 	}
@@ -122,16 +126,16 @@ namespace sqlpp
 			>
 			struct statement_t:
 				public Policies::template _member_t<detail::statement_policies_t<Db, Policies...>>...,
-				public detail::statement_policies_t<Db, Policies...>::_value_type::template expression_operators<statement_t<Db, Policies...>>,
+				public expression_operators<statement_t<Db, Policies...>, value_type_of<detail::statement_policies_t<Db, Policies...>>>,
 				public detail::statement_policies_t<Db, Policies...>::_result_methods_t,
 				public Policies::template _methods_t<detail::statement_policies_t<Db, Policies...>>...
 	{
 		using _policies_t = typename detail::statement_policies_t<Db, Policies...>;
 
 		using _traits = make_traits<value_type_of<_policies_t>,
-					::sqlpp::tag::is_select, 
+					tag::is_select, 
 					tag_if<tag::is_expression, is_expression_t<_policies_t>::value>, 
-					tag_if<tag::is_named_expression, is_expression_t<_policies_t>::value>,
+					tag_if<tag::is_selectable, is_expression_t<_policies_t>::value>,
 					tag::requires_braces>;
 		using _recursive_traits = typename _policies_t::_recursive_traits;
 		using _used_outer_tables = typename _policies_t::_all_provided_outer_tables;
@@ -184,7 +188,7 @@ namespace sqlpp
 		struct serializer_t<Context, statement_t<Database, Policies...>>
 		{
 			using T = statement_t<Database, Policies...>;
-			using P = ::sqlpp::detail::statement_policies_t<Database, Policies...>;
+			using P = detail::statement_policies_t<Database, Policies...>;
 
 			static Context& _(const T& t, Context& context)
 			{
@@ -198,7 +202,7 @@ namespace sqlpp
 	template<typename NameData>
 		struct statement_name_t
 		{
-			using _traits = make_traits<no_value_t, ::sqlpp::tag::is_noop>;
+			using _traits = make_traits<no_value_t, tag::is_noop>;
 			using _recursive_traits = make_recursive_traits<>;
 
 			// Data

include/sqlpp11/sum.h

@@ -32,13 +32,14 @@
 namespace sqlpp
 {
 	template<typename Flag, typename Expr>
-		struct sum_t: public value_type_of<Expr>::template expression_operators<sum_t<Flag, Expr>>,
+		struct sum_t:
+			public expression_operators<sum_t<Flag, Expr>, value_type_of<Expr>>,
 			public alias_operators<sum_t<Flag, Expr>>
 	{
-		using _traits = make_traits<value_type_of<Expr>, ::sqlpp::tag::is_expression, ::sqlpp::tag::is_named_expression>;
-		using _recursive_traits = make_recursive_traits<Expr>;
+		using _traits = make_traits<value_type_of<Expr>, tag::is_expression, tag::is_selectable>;
+		using _recursive_traits = make_recursive_traits<Expr, aggregate_function>;
 
-		static_assert(is_noop<Flag>::value or std::is_same<sqlpp::distinct_t, Flag>::value, "sum() used with flag other than 'distinct'");
+		static_assert(is_noop<Flag>::value or std::is_same<distinct_t, Flag>::value, "sum() used with flag other than 'distinct'");
 		static_assert(is_numeric_t<Expr>::value, "sum() requires a numeric expression as argument");
 
 		struct _name_t
@@ -74,7 +75,7 @@ namespace sqlpp
 			static Context& _(const T& t, Context& context)
 			{
 				context << "SUM(";
-				if (std::is_same<sqlpp::distinct_t, Flag>::value)
+				if (std::is_same<distinct_t, Flag>::value)
 				{
 					serialize(Flag(), context);
 					context << ' ';
@@ -88,13 +89,15 @@ namespace sqlpp
 	template<typename T>
 		auto sum(T t) -> sum_t<noop, wrap_operand_t<T>>
 		{
+			static_assert(not contains_aggregate_function_t<wrap_operand_t<T>>::value, "sum() cannot be used on an aggregate function");
 			static_assert(is_numeric_t<wrap_operand_t<T>>::value, "sum() requires a numeric expression as argument");
 			return { t };
 		}
 
 	template<typename T>
-		auto sum(const sqlpp::distinct_t&, T t) -> sum_t<sqlpp::distinct_t, wrap_operand_t<T>>
+		auto sum(const distinct_t&, T t) -> sum_t<distinct_t, wrap_operand_t<T>>
 		{
+			static_assert(not contains_aggregate_function_t<wrap_operand_t<T>>::value, "sum() cannot be used on an aggregate function");
 			static_assert(is_numeric_t<wrap_operand_t<T>>::value, "sum() requires a numeric expression as argument");
 			return { t };
 		}

include/sqlpp11/table.h

@@ -40,7 +40,9 @@ namespace sqlpp
 	struct table_base_t {};
 
 	template<typename Table, typename... ColumnSpec>
-		struct table_t: public table_base_t, public ColumnSpec::_name_t::template _member_t<column_t<Table, ColumnSpec>>...
+		struct table_t: 
+			public table_base_t, 
+			public member_t<ColumnSpec, column_t<Table, ColumnSpec>>...
 	{
 		using _traits = make_traits<no_value_t, tag::is_table>;
 
@@ -51,7 +53,7 @@ namespace sqlpp
 			using _provided_tables = detail::type_set<Table>;
 			using _provided_outer_tables = detail::type_set<>;
 			using _extra_tables = detail::type_set<>;
-			using _can_be_null = std::false_type;
+			using _tags = detail::type_set<>;
 		};
 
 		static_assert(sizeof...(ColumnSpec), "at least one column required per table");
@@ -62,31 +64,31 @@ namespace sqlpp
 
 
 		template<typename T>
-			join_t<inner_join_t, Table, T> join(T t)
+			join_t<inner_join_t, Table, T> join(T t) const
 			{
 				return { *static_cast<const Table*>(this), t };
 			}
 
 		template<typename T>
-			join_t<inner_join_t, Table, T> inner_join(T t)
+			join_t<inner_join_t, Table, T> inner_join(T t) const
 			{
 				return { *static_cast<const Table*>(this), t };
 			}
 
 		template<typename T>
-			join_t<outer_join_t, Table, T> outer_join(T t)
+			join_t<outer_join_t, Table, T> outer_join(T t) const
 			{
 				return { *static_cast<const Table*>(this), t };
 			}
 
 		template<typename T>
-			join_t<left_outer_join_t, Table, T> left_outer_join(T t)
+			join_t<left_outer_join_t, Table, T> left_outer_join(T t) const
 			{
 				return { *static_cast<const Table*>(this), t };
 			}
 
 		template<typename T>
-			join_t<right_outer_join_t, Table, T> right_outer_join(T t)
+			join_t<right_outer_join_t, Table, T> right_outer_join(T t) const
 			{
 				return { *static_cast<const Table*>(this), t };
 			}

include/sqlpp11/table_alias.h

@@ -36,10 +36,11 @@
 namespace sqlpp
 {
 	template<typename AliasProvider, typename Table, typename... ColumnSpec>
-		struct table_alias_t: public ColumnSpec::_name_t::template _member_t<column_t<AliasProvider, ColumnSpec>>...
+		struct table_alias_t:
+			public member_t<ColumnSpec, column_t<AliasProvider, ColumnSpec>>...
 	{
 		//FIXME: Need to add join functionality
-		using _traits = make_traits<value_type_of<Table>, tag::is_table, tag::is_alias, tag_if<tag::is_named_expression, is_expression_t<Table>::value>>;
+		using _traits = make_traits<value_type_of<Table>, tag::is_table, tag::is_alias, tag_if<tag::is_selectable, is_expression_t<Table>::value>>;
 
 		struct _recursive_traits
 		{
@@ -48,13 +49,13 @@ namespace sqlpp
 			using _provided_tables = detail::type_set<AliasProvider>;
 			using _provided_outer_tables = detail::type_set<>;
 			using _extra_tables = detail::type_set<>;
-			using _can_be_null = std::false_type;
+			using _tags = detail::type_set<>;
 		};
 
 		static_assert(required_tables_of<Table>::size::value == 0, "table aliases must not depend on external tables");
 
 		using _name_t = typename AliasProvider::_name_t;
-		using _column_tuple_t = std::tuple<column_t<Table, ColumnSpec>...>;
+		using _column_tuple_t = std::tuple<column_t<AliasProvider, ColumnSpec>...>;
 
 		table_alias_t(Table table):
 			_table(table)

include/sqlpp11/text.h

@@ -39,32 +39,39 @@ namespace sqlpp
 	// text value type
 	struct text
 	{
-		using _traits = make_traits<text, ::sqlpp::tag::is_text, ::sqlpp::tag::is_value_type>;
-		using _tag = ::sqlpp::tag::is_text;
+		using _traits = make_traits<text, tag::is_value_type>;
+		using _tag = tag::is_text;
 		using _cpp_value_type = std::string;
 
-		struct _parameter_t
+		template<typename T>
+			using _is_valid_operand = is_text_t<T>;
+	};
+
+	// text parameter type
+	template<>
+		struct parameter_value_t<text>
 		{
 			using _value_type = text;
+			using _cpp_value_type = typename _value_type::_cpp_value_type;
 
-			_parameter_t():
+			parameter_value_t():
 				_value(""),
 				_is_null(true)
 			{}
 
-			_parameter_t(const _cpp_value_type& value):
+			parameter_value_t(const _cpp_value_type& value):
 				_value(value),
 				_is_null(false)
 			{}
 
-			_parameter_t& operator=(const _cpp_value_type& value)
+			parameter_value_t& operator=(const _cpp_value_type& value)
 			{
 				_value = value;
 				_is_null = false;
 				return *this;
 			}
 
-			_parameter_t& operator=(const tvin_t<wrap_operand_t<_cpp_value_type>>& t)
+			parameter_value_t& operator=(const tvin_t<wrap_operand_t<_cpp_value_type>>& t)
 			{
 				if (t._is_trivial())
 				{
@@ -79,7 +86,7 @@ namespace sqlpp
 				return *this;
 			}
 
-			_parameter_t& operator=(const std::nullptr_t&)
+			parameter_value_t& operator=(const std::nullptr_t&)
 			{
 				_value = "";
 				_is_null = true;
@@ -110,18 +117,13 @@ namespace sqlpp
 		};
 
 
-		template<typename T>
-			struct _is_valid_operand
-			{
-				static constexpr bool value = 
-					is_expression_t<T>::value // expressions are OK
-					and is_text_t<T>::value // the correct value type is required, of course
-					;
-			};
-
+	// text expression operators
 	template<typename Base>
-			struct expression_operators: public basic_expression_operators<Base, is_text_t>
+		struct expression_operators<Base, text>: public basic_expression_operators<Base, text>
 	{
+		template<typename T>
+			using _is_valid_operand = is_valid_operand<text, T>;
+
 		template<typename T>
 			concat_t<Base, wrap_operand_t<T>> operator+(T t) const
 			{
@@ -141,20 +143,24 @@ namespace sqlpp
 			}
 	};
 
+	// text column operators
 	template<typename Base>
-			struct column_operators
+		struct column_operators<Base, text>
 		{
+			template<typename T>
+				using _is_valid_operand = is_valid_operand<text, T>;
+
 			template<typename T>
 				auto operator +=(T t) const -> assignment_t<Base, concat_t<Base, wrap_operand_t<T>>>
 				{
 					using rhs = wrap_operand_t<T>;
 					static_assert(_is_valid_operand<rhs>::value, "invalid rhs assignment operand");
 
-						return { *static_cast<const Base*>(this), { *static_cast<const Base*>(this), rhs{t} } };
+					return { *static_cast<const Base*>(this), concat_t<Base, wrap_operand_t<T>>{ *static_cast<const Base*>(this), rhs{t} } };
 				}
 		};
-	};
 
+	// text result field
 	template<typename Db, typename FieldSpec>
 		struct result_field_t<text, Db, FieldSpec>: public result_field_methods_t<result_field_t<text, Db, FieldSpec>>
 	{

include/sqlpp11/type_traits.h

@@ -32,30 +32,59 @@
 
 namespace sqlpp
 {
+	namespace tag
+	{
+		struct can_be_null{};
+		struct contains_aggregate_function{};
+	};
+
 	namespace detail
 	{
 		template<typename T, typename Enable = void>
 		struct can_be_null_impl { using type = std::false_type; };
 		template<typename T>
-		struct can_be_null_impl<T, typename std::enable_if<T::_recursive_traits::_can_be_null::value>::type> { using type = std::true_type; };
+		struct can_be_null_impl<T, typename std::enable_if<is_element_of<tag::can_be_null, typename T::_recursive_traits::_tags>::value>::type> { using type = std::true_type; };
 	}
 	template<typename T>
 	using can_be_null_t = typename detail::can_be_null_impl<T>::type;
 
-	namespace tag\
-	{\
-		struct can_be_null{};\
-	};\
-	namespace detail\
-	{\
-		template<typename T, typename Enable = void>\
-		struct column_spec_can_be_null_impl { using type = std::false_type; };\
-		template<typename T>\
-		struct column_spec_can_be_null_impl<T, typename std::enable_if<detail::is_element_of<tag::can_be_null, typename T::_traits::_tags>::value>::type> { using type = std::true_type; };\
-	}\
-	template<typename T>\
+	namespace detail
+	{
+		template<typename T, typename Enable = void>
+		struct contains_aggregate_function_impl { using type = std::false_type; };
+		template<typename T>
+		struct contains_aggregate_function_impl<T, typename std::enable_if<is_element_of<tag::contains_aggregate_function, typename T::_recursive_traits::_tags>::value>::type> { using type = std::true_type; };
+	}
+	template<typename T>
+	using contains_aggregate_function_t = typename detail::contains_aggregate_function_impl<T>::type;
+
+	namespace detail
+	{
+		template<typename T, typename Enable = void>
+		struct column_spec_can_be_null_impl { using type = std::false_type; };
+		template<typename T>
+		struct column_spec_can_be_null_impl<T, typename std::enable_if<detail::is_element_of<tag::can_be_null, typename T::_traits::_tags>::value>::type> { using type = std::true_type; };
+	}
+	template<typename T>
 	using column_spec_can_be_null_t = typename detail::column_spec_can_be_null_impl<T>::type;
 
+	namespace tag
+	{
+		struct is_expression{};
+	};
+	namespace detail
+	{
+		template<typename T, typename Enable = void>
+		struct is_expression_impl { using type = std::false_type; };
+		template<typename T>
+		struct is_expression_impl<T, typename std::enable_if<
+					detail::is_element_of<tag::is_expression, typename T::_traits::_tags>::value
+					and not detail::is_element_of<tag::contains_aggregate_function, typename T::_recursive_traits::_tags>::value
+					>::type> { using type = std::true_type; };
+	}
+	template<typename T>
+	using is_expression_t = typename detail::is_expression_impl<T>::type;
+
 #define SQLPP_VALUE_TRAIT_GENERATOR(name) \
 	namespace tag\
 	{\
@@ -82,8 +111,7 @@ namespace sqlpp
 		detail::is_element_of<tag::is_floating_point, typename T::_traits::_tags>::value>;
 	SQLPP_VALUE_TRAIT_GENERATOR(is_text);
 	SQLPP_VALUE_TRAIT_GENERATOR(is_wrapped_value);
-	SQLPP_VALUE_TRAIT_GENERATOR(is_expression);
-	SQLPP_VALUE_TRAIT_GENERATOR(is_named_expression);
+	SQLPP_VALUE_TRAIT_GENERATOR(is_selectable);
 	SQLPP_VALUE_TRAIT_GENERATOR(is_multi_expression);
 	SQLPP_VALUE_TRAIT_GENERATOR(is_alias);
 	SQLPP_VALUE_TRAIT_GENERATOR(is_select_flag);
@@ -140,80 +168,35 @@ namespace sqlpp
 
 	namespace detail
 	{
-		template<typename T>
-			struct value_type_of_impl
-			{
-				using type = typename T::_traits::_value_type;
-			};
-
-		template<typename T>
-			struct required_table_of_impl
-			{
-				using type = typename T::_recursive_traits::_required_tables;
-			};
-
-		template<typename T>
-			struct provided_table_of_impl
-			{
-				using type = typename T::_recursive_traits::_provided_tables;
-			};
-
-		template<typename T>
-			struct provided_outer_table_of_impl
-			{
-				using type = typename T::_recursive_traits::_provided_outer_tables;
-			};
-
-		template<typename T>
-			struct extra_table_of_impl
-			{
-				using type = typename T::_recursive_traits::_extra_tables;
-			};
-
-		template<typename T>
-			struct parameters_of_impl
-			{
-				using type = typename T::_recursive_traits::_parameters;
-			};
-
-		template<typename T>
-			struct name_of_impl
-			{
-				using type = typename T::_name_t;
-			};
-
 		template<typename... T>
-			struct make_parameter_tuple_impl
-			{
-				using type = decltype(std::tuple_cat(std::declval<T>()...));
-			};
-
-		template<typename... T>
-			using make_parameter_tuple_t = typename make_parameter_tuple_impl<T...>::type;
+			using make_parameter_tuple_t = decltype(std::tuple_cat(std::declval<T>()...));
 	}
 	template<typename T>
-		using value_type_of = typename detail::value_type_of_impl<T>::type;
+		using value_type_of = typename T::_traits::_value_type;
 
 	template<typename T>
 		using cpp_value_type_of = typename value_type_of<T>::_cpp_value_type;
 
 	template<typename T>
-		using required_tables_of = typename detail::required_table_of_impl<T>::type;
+		using required_tables_of = typename T::_recursive_traits::_required_tables;
 
 	template<typename T>
-		using provided_tables_of = typename detail::provided_table_of_impl<T>::type;
+		using provided_tables_of = typename T::_recursive_traits::_provided_tables;
 
 	template<typename T>
-		using provided_outer_tables_of = typename detail::provided_outer_table_of_impl<T>::type;
+		using provided_outer_tables_of = typename T::_recursive_traits::_provided_outer_tables;
 
 	template<typename T>
-		using extra_tables_of = typename detail::extra_table_of_impl<T>::type;
+		using extra_tables_of = typename T::_recursive_traits::_extra_tables;
 
 	template<typename T>
-		using parameters_of = typename detail::parameters_of_impl<T>::type;
+		using parameters_of = typename T::_recursive_traits::_parameters;
 
 	template<typename T>
-		using name_of = typename detail::name_of_impl<T>::type;
+		using recursive_tags_of = typename T::_recursive_traits::_tags;
+
+	template<typename T>
+		using name_of = typename T::_name_t;
 
 	template<typename ValueType, typename... Tags>
 		struct make_traits
@@ -221,6 +204,7 @@ namespace sqlpp
 			using _value_type = ValueType;
 			using _tags = detail::make_type_set_t<typename ValueType::_tag, Tags...>;
 		};
+
 	template<typename... Arguments>
 		struct make_recursive_traits
 		{
@@ -229,9 +213,31 @@ namespace sqlpp
 			using _provided_outer_tables = detail::make_joined_set_t<provided_outer_tables_of<Arguments>...>;
 			using _extra_tables = detail::make_joined_set_t<extra_tables_of<Arguments>...>;
 			using _parameters = detail::make_parameter_tuple_t<parameters_of<Arguments>...>;
-			using _can_be_null = detail::any_t<can_be_null_t<Arguments>::value...>;
+			using _tags = detail::make_joined_set_t<recursive_tags_of<Arguments>...>;
 		};
 
+	template<typename... Tags>
+		struct recursive_tags
+		{
+			using _required_tables = detail::type_set<>;
+			using _provided_tables = detail::type_set<>;
+			using _provided_outer_tables = detail::type_set<>;
+			using _extra_tables = detail::type_set<>;
+			using _parameters = std::tuple<>;
+			using _tags = detail::type_set<Tags...>;
+		};
+
+	struct aggregate_function
+	{
+		struct _traits { using _value_type = void; using _tags = detail::type_set<>; };
+		using _recursive_traits = recursive_tags<tag::contains_aggregate_function>;
+	};
+
+	template<typename NameProvider, typename Member>
+		using member_t = typename NameProvider::_name_t::template _member_t<Member>;
+
+	template<typename Policies>
+		using derived_statement_t = typename Policies::_statement_t;
 }
 
 #endif

include/sqlpp11/update.h

@@ -28,7 +28,7 @@
 #define SQLPP_UPDATE_H
 
 #include <sqlpp11/statement.h>
-
+#include <sqlpp11/connection.h>
 #include <sqlpp11/type_traits.h>
 #include <sqlpp11/parameter_list.h>
 #include <sqlpp11/prepared_update.h>
@@ -49,7 +49,7 @@ namespace sqlpp
 		template<typename Policies>
 			struct _result_methods_t
 			{
-				using _statement_t = typename Policies::_statement_t;
+				using _statement_t = derived_statement_t<Policies>;
 
 				const _statement_t& _get_statement() const
 				{
@@ -109,6 +109,7 @@ namespace sqlpp
 		constexpr auto  dynamic_update(const Database&, Table table)
 		-> decltype(blank_update_t<Database>().from(table))
 		{
+			static_assert(std::is_base_of<connection, Database>::value, "Invalid database parameter");
 			return { blank_update_t<Database>().from(table) };
 		}
 }

include/sqlpp11/update_list.h

@@ -56,7 +56,7 @@ namespace sqlpp
 	template<typename Database, typename... Assignments>
 		struct update_list_t
 		{
-			using _traits = make_traits<no_value_t, ::sqlpp::tag::is_update_list>;
+			using _traits = make_traits<no_value_t, tag::is_update_list>;
 			using _recursive_traits = make_recursive_traits<Assignments...>;
 			using _is_dynamic = is_database<Database>;
 
@@ -78,12 +78,12 @@ namespace sqlpp
 						{
 							static_assert(_is_dynamic::value, "add must not be called for static from()");
 							static_assert(is_assignment_t<Assignment>::value, "invalid assignment argument in add()");
-							using _assigned_columns = detail::make_type_set_t<typename Assignments::_lhs_t...>;
-							static_assert(not detail::is_element_of<typename Assignment::_lhs_t, _assigned_columns>::value, "Must not assign value to column twice");
-							static_assert(sqlpp::detail::not_t<must_not_update_t, typename Assignment::_lhs_t>::value, "add() argument must not be updated");
+							using _assigned_columns = detail::make_type_set_t<lhs_t<Assignments>...>;
+							static_assert(not detail::is_element_of<lhs_t<Assignment>, _assigned_columns>::value, "Must not assign value to column twice");
+							static_assert(detail::not_t<must_not_update_t, lhs_t<Assignment>>::value, "add() argument must not be updated");
 							static_assert(TableCheckRequired::value or Policies::template _no_unknown_tables<Assignment>::value, "assignment uses tables unknown to this statement in add()");
 
-							using ok = ::sqlpp::detail::all_t<
+							using ok = detail::all_t<
 								_is_dynamic::value, 
 								is_assignment_t<Assignment>::value>;
 
@@ -130,7 +130,7 @@ namespace sqlpp
 
 	struct no_update_list_t
 	{
-		using _traits = make_traits<no_value_t, ::sqlpp::tag::is_where>;
+		using _traits = make_traits<no_value_t, tag::is_where>;
 		using _recursive_traits = make_recursive_traits<>;
 
 		// Data
@@ -165,7 +165,7 @@ namespace sqlpp
 			{
 				using _database_t = typename Policies::_database_t;
 				template<typename T>
-					using _new_statement_t = typename Policies::template _new_statement_t<no_update_list_t, T>;
+					using _new_statement_t = new_statement<Policies, no_update_list_t, T>;
 
 				static void _check_consistency()
 				{
@@ -173,7 +173,7 @@ namespace sqlpp
 				}
 
 				template<typename... Assignments>
-					auto set(Assignments... assignments)
+					auto set(Assignments... assignments) const
 					-> _new_statement_t<update_list_t<void, Assignments...>>
 					{
 						static_assert(sizeof...(Assignments), "at least one assignment expression required in set()");
@@ -181,7 +181,7 @@ namespace sqlpp
 					}
 
 				template<typename... Assignments>
-					auto dynamic_set(Assignments... assignments)
+					auto dynamic_set(Assignments... assignments) const
 					-> _new_statement_t<update_list_t<_database_t, Assignments...>>
 					{
 						static_assert(not std::is_same<_database_t, void>::value, "dynamic_set() must not be called in a static statement");
@@ -190,17 +190,17 @@ namespace sqlpp
 
 			private:
 				template<typename Database, typename... Assignments>
-					auto _set_impl(Assignments... assignments)
+					auto _set_impl(Assignments... assignments) const
 					-> _new_statement_t<update_list_t<Database, Assignments...>>
 					{
-						static_assert(not ::sqlpp::detail::has_duplicates<Assignments...>::value, "at least one duplicate argument detected in set()");
-						static_assert(::sqlpp::detail::all_t<is_assignment_t<Assignments>::value...>::value, "at least one argument is not an assignment in set()");
-						static_assert(::sqlpp::detail::none_t<must_not_update_t<typename Assignments::_lhs_t>::value...>::value, "at least one assignment is prohibited by its column definition in set()");
+						static_assert(detail::all_t<is_assignment_t<Assignments>::value...>::value, "at least one argument is not an assignment in set()");
+						static_assert(not detail::has_duplicates<lhs_t<Assignments>...>::value, "at least one duplicate column detected in set()");
+						static_assert(detail::none_t<must_not_update_t<lhs_t<Assignments>>::value...>::value, "at least one assignment is prohibited by its column definition in set()");
 
-						using _column_required_tables = ::sqlpp::detail::make_joined_set_t<required_tables_of<typename Assignments::_lhs_t>...>;
+						using _column_required_tables = detail::make_joined_set_t<required_tables_of<lhs_t<Assignments>>...>;
 						static_assert(sizeof...(Assignments) ? (_column_required_tables::size::value == 1) : true, "set() contains assignments for columns from more than one table");
 
-						return { *static_cast<typename Policies::_statement_t*>(this), update_list_data_t<Database, Assignments...>{assignments...} };
+						return { static_cast<const derived_statement_t<Policies>&>(*this), update_list_data_t<Database, Assignments...>{assignments...} };
 					}
 			};
 	};

include/sqlpp11/using.h

@@ -57,16 +57,16 @@ namespace sqlpp
 	template<typename Database, typename... Tables>
 		struct using_t
 		{
-			using _traits = make_traits<no_value_t, ::sqlpp::tag::is_using_>;
+			using _traits = make_traits<no_value_t, tag::is_using_>;
 			using _recursive_traits = make_recursive_traits<Tables...>;
 
 			using _is_dynamic = is_database<Database>;
 
 			static_assert(_is_dynamic::value or sizeof...(Tables), "at least one table argument required in using()");
 
-			static_assert(not ::sqlpp::detail::has_duplicates<Tables...>::value, "at least one duplicate argument detected in using()");
+			static_assert(not detail::has_duplicates<Tables...>::value, "at least one duplicate argument detected in using()");
 
-			static_assert(::sqlpp::detail::all_t<is_table_t<Tables>::value...>::value, "at least one argument is not an table in using()");
+			static_assert(detail::all_t<is_table_t<Tables>::value...>::value, "at least one argument is not an table in using()");
 
 			// Data
 			using _data_t = using_data_t<Database, Tables...>;
@@ -81,7 +81,7 @@ namespace sqlpp
 							static_assert(_is_dynamic::value, "add must not be called for static using()");
 							static_assert(is_table_t<Table>::value, "invalid table argument in add()");
 
-							using ok = ::sqlpp::detail::all_t<_is_dynamic::value, is_table_t<Table>::value>;
+							using ok = detail::all_t<_is_dynamic::value, is_table_t<Table>::value>;
 
 							_add_impl(table, ok()); // dispatch to prevent compile messages after the static_assert
 						}
@@ -128,7 +128,7 @@ namespace sqlpp
 	// NO USING YET
 	struct no_using_t
 	{
-		using _traits = make_traits<no_value_t, ::sqlpp::tag::is_where>;
+		using _traits = make_traits<no_value_t, tag::is_where>;
 		using _recursive_traits = make_recursive_traits<>;
 
 		// Data
@@ -163,23 +163,23 @@ namespace sqlpp
 			{
 				using _database_t = typename Policies::_database_t;
 				template<typename T>
-					using _new_statement_t = typename Policies::template _new_statement_t<no_using_t, T>;
+					using _new_statement_t = new_statement<Policies, no_using_t, T>;
 
 				static void _check_consistency() {}
 
 				template<typename... Args>
-					auto using_(Args... args)
+					auto using_(Args... args) const
 					-> _new_statement_t<using_t<void, Args...>>
 					{
-						return { *static_cast<typename Policies::_statement_t*>(this), using_data_t<void, Args...>{args...} };
+						return { static_cast<const derived_statement_t<Policies>&>(*this), using_data_t<void, Args...>{args...} };
 					}
 
 				template<typename... Args>
-					auto dynamic_using(Args... args)
+					auto dynamic_using(Args... args) const
 					-> _new_statement_t<using_t<_database_t, Args...>>
 					{
 						static_assert(not std::is_same<_database_t, void>::value, "dynamic_using must not be called in a static statement");
-						return { *static_cast<typename Policies::_statement_t*>(this), using_data_t<_database_t, Args...>{args...} };
+						return { static_cast<const derived_statement_t<Policies>&>(*this), using_data_t<_database_t, Args...>{args...} };
 					}
 			};
 	};

include/sqlpp11/value_type_fwd.h

@@ -0,0 +1,65 @@
+/*
+ * Copyright (c) 2013-2014, Roland Bock
+ * All rights reserved.
+ * 
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ * 
+ *   Redistributions of source code must retain the above copyright notice, this
+ *   list of conditions and the following disclaimer.
+ * 
+ *   Redistributions in binary form must reproduce the above copyright notice, this
+ *   list of conditions and the following disclaimer in the documentation and/or
+ *   other materials provided with the distribution.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
+ * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef SQLPP_VALUE_TYPE_FWD_H
+#define SQLPP_VALUE_TYPE_FWD_H
+
+#include <sqlpp11/wrong.h>
+#include <sqlpp11/type_traits.h>
+
+namespace sqlpp
+{
+	template<typename ValueType>
+		struct parameter_value_t
+		{
+			static_assert(wrong_t<parameter_value_t>::value, "Missing parameter value type for ValueType");
+		};
+
+	template<typename Column, typename ValueType>
+		struct column_operators
+		{
+			static_assert(wrong_t<column_operators>::value, "Missing column operators for ValueType");
+		};
+
+	template<typename Expr, typename ValueType>
+		struct expression_operators
+		{
+			static_assert(wrong_t<expression_operators>::value, "Missing expression operators for ValueType");
+		};
+
+	template<typename ValueType, typename T>
+		struct is_valid_operand
+		{
+			static constexpr bool value = 
+				is_expression_t<T>::value // expressions are OK
+				and ValueType::template _is_valid_operand<T>::value // the correct value type is required, of course
+				;
+		};
+}
+
+#endif
+
+

include/sqlpp11/verbatim.h

@@ -0,0 +1,76 @@
+/*
+ * Copyright (c) 2013-2014, Roland Bock
+ * All rights reserved.
+ * 
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ * 
+ *   Redistributions of source code must retain the above copyright notice, this
+ *   list of conditions and the following disclaimer.
+ * 
+ *   Redistributions in binary form must reproduce the above copyright notice, this
+ *   list of conditions and the following disclaimer in the documentation and/or
+ *   other materials provided with the distribution.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
+ * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef SQLPP_VERBATIM_H
+#define SQLPP_VERBATIM_H
+
+#include <sqlpp11/type_traits.h>
+#include <sqlpp11/serialize.h>
+
+namespace sqlpp
+{
+	template<typename ValueType> // Csaba Csoma suggests: unsafe_sql instead of verbatim
+		struct verbatim_t:
+			public expression_operators<verbatim_t<ValueType>, ValueType>,
+			public alias_operators<verbatim_t<ValueType>>
+	{
+		using _traits = make_traits<ValueType, tag::is_expression>;
+		struct _recursive_traits : public make_recursive_traits<>
+		{
+			using _tags = detail::type_set<tag::can_be_null>; // since we do not know what's going on inside the verbatim, we assume it can be null
+		};
+
+		verbatim_t(std::string verbatim): _verbatim(verbatim) {}
+		verbatim_t(const verbatim_t&) = default;
+		verbatim_t(verbatim_t&&) = default;
+		verbatim_t& operator=(const verbatim_t&) = default;
+		verbatim_t& operator=(verbatim_t&&) = default;
+		~verbatim_t() = default;
+
+		std::string _verbatim;
+	};
+
+	template<typename Context, typename ValueType>
+		struct serializer_t<Context, verbatim_t<ValueType>>
+		{
+			using T = verbatim_t<ValueType>;
+
+			static Context& _(const T& t, Context& context)
+			{
+				context << t._verbatim;
+				return context;
+			}
+		};
+
+	template<typename ValueType, typename StringType>
+		auto verbatim(StringType s) -> verbatim_t<ValueType>
+		{
+			return { s };
+		}
+
+}
+
+#endif

include/sqlpp11/verbatim_table.h

@@ -46,9 +46,9 @@ namespace sqlpp
 		};
 	}
 
-	struct verbatim_table_t: public sqlpp::table_t<verbatim_table_t, detail::unusable_pseudo_column_t>
+	struct verbatim_table_t: public table_t<verbatim_table_t, detail::unusable_pseudo_column_t>
 	{
-		struct _recursive_traits: public sqlpp::table_t<verbatim_table_t, detail::unusable_pseudo_column_t>::_recursive_traits
+		struct _recursive_traits: public table_t<verbatim_table_t, detail::unusable_pseudo_column_t>::_recursive_traits
 		{
 			using _provided_outer_tables = detail::type_set<verbatim_table_t>;
 		};

include/sqlpp11/where.h

@@ -58,14 +58,14 @@ namespace sqlpp
 	template<typename Database, typename... Expressions>
 		struct where_t
 		{
-			using _traits = make_traits<no_value_t, ::sqlpp::tag::is_where>;
+			using _traits = make_traits<no_value_t, tag::is_where>;
 			using _recursive_traits = make_recursive_traits<Expressions...>;
 
 			using _is_dynamic = is_database<Database>;
 
 			static_assert(_is_dynamic::value or sizeof...(Expressions), "at least one expression argument required in where()");
-			static_assert(sqlpp::detail::none_t<is_assignment_t<Expressions>::value...>::value, "at least one argument is an assignment in where()");
-			static_assert(sqlpp::detail::all_t<is_expression_t<Expressions>::value...>::value, "at least one argument is not valid expression in where()");
+			static_assert(detail::none_t<is_assignment_t<Expressions>::value...>::value, "at least one argument is an assignment in where()");
+			static_assert(detail::all_t<is_expression_t<Expressions>::value...>::value, "at least one argument is not valid expression in where()");
 
 			// Data
 			using _data_t = where_data_t<Database, Expressions...>;
@@ -87,7 +87,7 @@ namespace sqlpp
 							static_assert(is_expression_t<Expression>::value, "invalid expression argument in where::add()");
 							static_assert(not TableCheckRequired::value or Policies::template _no_unknown_tables<Expression>::value, "expression uses tables unknown to this statement in where::add()");
 
-							using ok = ::sqlpp::detail::all_t<_is_dynamic::value, is_expression_t<Expression>::value>;
+							using ok = detail::all_t<_is_dynamic::value, is_expression_t<Expression>::value>;
 
 							_add_impl(expression, ok()); // dispatch to prevent compile messages after the static_assert
 						}
@@ -141,7 +141,7 @@ namespace sqlpp
 	template<>
 		struct where_t<void, bool>
 		{
-			using _traits = make_traits<no_value_t, ::sqlpp::tag::is_where>;
+			using _traits = make_traits<no_value_t, tag::is_where>;
 			using _recursive_traits = make_recursive_traits<>;
 
 			// Data
@@ -181,10 +181,10 @@ namespace sqlpp
 		};
 
 	// NO WHERE YET
-	template<bool Required>
+	template<bool WhereRequired>
 		struct no_where_t
 		{
-			using _traits = make_traits<no_value_t, ::sqlpp::tag::is_where>;
+			using _traits = make_traits<no_value_t, tag::is_where>;
 			using _recursive_traits = make_recursive_traits<>;
 
 			// Data
@@ -220,26 +220,28 @@ namespace sqlpp
 				{
 					using _database_t = typename Policies::_database_t;
 					template<typename T>
-						using _new_statement_t = typename Policies::template _new_statement_t<no_where_t, T>;
+						using _new_statement_t = new_statement<Policies, no_where_t, T>;
 
 					static void _check_consistency()
 					{
-						static_assert(Required ? wrong_t<_methods_t>::value : true, "where expression required, e.g. where(true)");
+						static constexpr bool _tables_provided = (Policies::_all_provided_tables::size::value > 0);
+						static constexpr bool _required = WhereRequired and _tables_provided;
+						static_assert(not _required, "where expression required, e.g. where(true)");
 					}
 
 					template<typename... Args>
-						auto where(Args... args)
+						auto where(Args... args) const
 						-> _new_statement_t<where_t<void, Args...>>
 						{
-							return { *static_cast<typename Policies::_statement_t*>(this), where_data_t<void, Args...>{args...} };
+							return { static_cast<const derived_statement_t<Policies>&>(*this), where_data_t<void, Args...>{args...} };
 						}
 
 					template<typename... Args>
-						auto dynamic_where(Args... args)
+						auto dynamic_where(Args... args) const
 						-> _new_statement_t<where_t<_database_t, Args...>>
 						{
 							static_assert(not std::is_same<_database_t, void>::value, "dynamic_where must not be called in a static statement");
-							return { *static_cast<typename Policies::_statement_t*>(this), where_data_t<_database_t, Args...>{args...} };
+							return { static_cast<const derived_statement_t<Policies>&>(*this), where_data_t<_database_t, Args...>{args...} };
 						}
 				};
 		};

include/sqlpp11/wrap_operand.h

@@ -28,8 +28,10 @@
 #define SQLPP_DETAIL_WRAP_OPERAND_H
 
 #include <string>
+#include <sqlpp11/wrap_operand_fwd.h>
 #include <sqlpp11/serializer.h>
 #include <sqlpp11/type_traits.h>
+#include <sqlpp11/basic_expression_operators.h>
 
 namespace sqlpp
 {
@@ -38,9 +40,9 @@ namespace sqlpp
 	struct floating_point;
 	struct text;
 
-	struct boolean_operand
+	struct boolean_operand: public alias_operators<boolean_operand>
 	{
-		using _traits = make_traits<::sqlpp::boolean, ::sqlpp::tag::is_expression, ::sqlpp::tag::is_wrapped_value>;
+		using _traits = make_traits<boolean, tag::is_expression, tag::is_wrapped_value>;
 		using _recursive_traits = make_recursive_traits<>;
 
 		using _value_t = bool;
@@ -76,9 +78,9 @@ namespace sqlpp
 			}
 		};
 
-	struct integral_operand
+	struct integral_operand: public alias_operators<integral_operand>
 	{
-		using _traits = make_traits<::sqlpp::integral, ::sqlpp::tag::is_expression, ::sqlpp::tag::is_wrapped_value>;
+		using _traits = make_traits<integral, tag::is_expression, tag::is_wrapped_value>;
 		using _recursive_traits = make_recursive_traits<>;
 
 		using _value_t = int64_t;
@@ -115,9 +117,9 @@ namespace sqlpp
 		};
 
 
-	struct floating_point_operand
+	struct floating_point_operand: public alias_operators<floating_point_operand>
 	{
-		using _traits = make_traits<::sqlpp::floating_point, ::sqlpp::tag::is_expression, ::sqlpp::tag::is_wrapped_value>;
+		using _traits = make_traits<floating_point, tag::is_expression, tag::is_wrapped_value>;
 		using _recursive_traits = make_recursive_traits<>;
 
 		using _value_t = double;
@@ -153,9 +155,9 @@ namespace sqlpp
 			}
 		};
 
-	struct text_operand
+	struct text_operand: public alias_operators<text_operand>
 	{
-		using _traits = make_traits<::sqlpp::text, ::sqlpp::tag::is_expression, ::sqlpp::tag::is_wrapped_value>;
+		using _traits = make_traits<text, tag::is_expression, tag::is_wrapped_value>;
 		using _recursive_traits = make_recursive_traits<>;
 
 		using _value_t = std::string;
@@ -191,7 +193,7 @@ namespace sqlpp
 			}
 		};
 
-	template<typename T, typename Enable = void>
+	template<typename T, typename Enable>
 		struct wrap_operand
 		{
 			using type = T;
@@ -221,11 +223,6 @@ namespace sqlpp
 			using type = text_operand;
 		};
 
-	// FIXME: Need to allow std::ref arguments
-
-	template<typename T>
-		using wrap_operand_t = typename wrap_operand<T>::type;
-
 }
 
 #endif

include/sqlpp11/wrap_operand_fwd.h

@@ -0,0 +1,40 @@
+/*
+ * Copyright (c) 2013-2014, Roland Bock
+ * All rights reserved.
+ * 
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ * 
+ *   Redistributions of source code must retain the above copyright notice, this
+ *   list of conditions and the following disclaimer.
+ * 
+ *   Redistributions in binary form must reproduce the above copyright notice, this
+ *   list of conditions and the following disclaimer in the documentation and/or
+ *   other materials provided with the distribution.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
+ * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef SQLPP_DETAIL_WRAP_OPERAND_FWD_H
+#define SQLPP_DETAIL_WRAP_OPERAND_FWD_H
+
+namespace sqlpp
+{
+	template<typename T, typename Enable = void>
+		struct wrap_operand;
+
+	template<typename T>
+		using wrap_operand_t = typename wrap_operand<T>::type;
+
+}
+
+#endif

scripts/ddl2cpp

@@ -175,7 +175,6 @@ for tableCreation in tableCreations:
 
     print('  struct ' + tableClass + ': ' + NAMESPACE + '::table_t<' + tableTemplateParameters + '>', file=header)
     print('  {', file=header)
-    print('    using _value_type = ' + NAMESPACE + '::no_value_t;', file=header)
     print('    struct _name_t', file=header)
     print('    {', file=header)
     print('      static constexpr const char* _get_name() { return "' + sqlTableName + '"; }', file=header)

test_constraints/CMakeLists.txt

@@ -1,31 +1,33 @@
-include_directories(${CMAKE_BINARY_DIR}/tests)
+include_directories("${CMAKE_SOURCE_DIR}/tests")
 
 add_custom_target(test_sqlpp_constraints COMMAND true)
 
 function(test_constraint name pattern)
 
 	add_executable(
-		${name}
+		"${name}"
 		EXCLUDE_FROM_ALL
-		${name}.cpp
+		"${name}.cpp"
 		)
 
-	add_custom_command(OUTPUT ${name}.out
-				COMMAND ${CMAKE_MAKE_PROGRAM} ${name} > ${CMAKE_CURRENT_BINARY_DIR}/${name}.out 2>&1  || true
-				COMMAND grep ${pattern} ${CMAKE_CURRENT_BINARY_DIR}/${name}.out > /dev/null
-				DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/${name}.cpp
+	add_custom_command(OUTPUT "${name}.out"
+				COMMAND "${CMAKE_MAKE_PROGRAM}" "${name}" > "${CMAKE_CURRENT_BINARY_DIR}/${name}.out" 2>&1  || true
+				COMMAND grep "${pattern}" "${CMAKE_CURRENT_BINARY_DIR}/${name}.out" > /dev/null
+				DEPENDS "${CMAKE_CURRENT_SOURCE_DIR}/${name}.cpp"
 				COMMENT "${name}"
-				)
+				VERBATIM)
 
-	add_custom_target(test_${name} DEPENDS ${name}.out COMMAND true)
+	add_custom_target("test_${name}" DEPENDS "${name}.out" COMMAND true)
 
 
-	add_dependencies(test_sqlpp_constraints test_${name})
-
-endfunction(testconstraint)
+	add_dependencies(test_sqlpp_constraints "test_${name}")
 
+endfunction(test_constraint)
 
+test_constraint(count_of_count "requires an expression as argument")
+test_constraint(max_of_max "requires an expression as argument")
 test_constraint(no_conversion_operator_if_null_not_trivial "int i = row.alpha")
 test_constraint(require_insert "required column is missing")
 test_constraint(must_not_insert "one assignment is prohibited")
+test_constraint(must_not_update "one assignment is prohibited")
 

test_constraints/count_of_count.cpp

@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) 2013-2014, Roland Bock
+ * All rights reserved.
+ * 
+ * Redistribution and use in source and binary forms, with or without modification, 
+ * are permitted provided that the following conditions are met:
+ * 
+ *  * Redistributions of source code must retain the above copyright notice, 
+ *    this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright notice, 
+ *    this list of conditions and the following disclaimer in the documentation 
+ *    and/or other materials provided with the distribution.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND 
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 
+ * IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE 
+ * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "Sample.h"
+#include "MockDb.h"
+#include <sqlpp11/functions.h>
+#include <iostream>
+
+MockDb db;
+
+int main()
+{
+	test::TabBar t;
+
+	count(count(t.alpha));
+}

test_constraints/max_of_max.cpp

@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) 2013-2014, Roland Bock
+ * All rights reserved.
+ * 
+ * Redistribution and use in source and binary forms, with or without modification, 
+ * are permitted provided that the following conditions are met:
+ * 
+ *  * Redistributions of source code must retain the above copyright notice, 
+ *    this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright notice, 
+ *    this list of conditions and the following disclaimer in the documentation 
+ *    and/or other materials provided with the distribution.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND 
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 
+ * IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE 
+ * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "Sample.h"
+#include "MockDb.h"
+#include <sqlpp11/functions.h>
+#include <iostream>
+
+MockDb db;
+
+int main()
+{
+	test::TabBar t;
+
+	max(max(t.alpha));
+}

test_constraints/must_not_update.cpp

@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) 2013-2014, Roland Bock
+ * All rights reserved.
+ * 
+ * Redistribution and use in source and binary forms, with or without modification, 
+ * are permitted provided that the following conditions are met:
+ * 
+ *  * Redistributions of source code must retain the above copyright notice, 
+ *    this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright notice, 
+ *    this list of conditions and the following disclaimer in the documentation 
+ *    and/or other materials provided with the distribution.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND 
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 
+ * IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE 
+ * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "Sample.h"
+#include "MockDb.h"
+#include <sqlpp11/update.h>
+
+MockDb db;
+
+int main()
+{
+	test::TabBar t;
+
+	update(t).set(t.alpha = 7, t.gamma = false, t.beta = "alpha must not be set");
+}

tests/CMakeLists.txt

@@ -1,9 +1,9 @@
 
 macro (build_and_run arg)
 	# Add headers to sources to enable file browsing in IDEs
-	include_directories(${CMAKE_BINARY_DIR}/tests)
-	add_executable(${arg} ${arg}.cpp ${sqlpp_headers} ${CMAKE_CURRENT_LIST_DIR}/Sample.h)
-	add_test(${arg} ${arg})
+	include_directories("${CMAKE_BINARY_DIR}/tests")
+	add_executable("${arg}" "${arg}.cpp" ${sqlpp_headers} "${CMAKE_CURRENT_LIST_DIR}/Sample.h")
+	add_test("${arg}" "${arg}")
 endmacro ()
 
 build_and_run(BooleanExpressionTest)
@@ -21,8 +21,7 @@ build_and_run(ResultTest)
 # if you want to use the generator, you can do something like this:
 #find_package(PythonInterp REQUIRED)
 #add_custom_command(
-#	OUTPUT ${CMAKE_CURRENT_LIST_DIR}/Sample.h 
-#	COMMAND ${PYTHON_EXECUTABLE} ${CMAKE_SOURCE_DIR}/scripts/ddl2cpp ${CMAKE_CURRENT_LIST_DIR}/sample.sql Sample test
-#	DEPENDS ${CMAKE_CURRENT_LIST_DIR}/sample.sql
-#	)
-
+#	OUTPUT "${CMAKE_CURRENT_LIST_DIR}/Sample.h"
+#	COMMAND "${PYTHON_EXECUTABLE}" "${CMAKE_SOURCE_DIR}/scripts/ddl2cpp" "${CMAKE_CURRENT_LIST_DIR}/sample.sql" Sample test
+#	DEPENDS "${CMAKE_CURRENT_LIST_DIR}/sample.sql"
+#	VERBATIM)

tests/FunctionTest.cpp

@@ -50,15 +50,15 @@ int main()
 		using TI = decltype(t.alpha.in(1, 2, 3));
 		using TF = decltype(f.omega.in(1.0, 2.0, 3.0));
 		using TT = decltype(t.beta.in("a", "b", "c"));
-		static_assert(sqlpp::is_named_expression_t<TI>::value, "type requirement");
+		static_assert(sqlpp::is_selectable_t<TI>::value, "type requirement");
 		static_assert(sqlpp::is_boolean_t<TI>::value, "type requirement");
 		static_assert(not sqlpp::is_numeric_t<TI>::value, "type requirement");
 		static_assert(not sqlpp::is_text_t<TI>::value, "type requirement");
-		static_assert(sqlpp::is_named_expression_t<TF>::value, "type requirement");
+		static_assert(sqlpp::is_selectable_t<TF>::value, "type requirement");
 		static_assert(sqlpp::is_boolean_t<TF>::value, "type requirement");
 		static_assert(not sqlpp::is_numeric_t<TF>::value, "type requirement");
 		static_assert(not sqlpp::is_text_t<TF>::value, "type requirement");
-		static_assert(sqlpp::is_named_expression_t<TF>::value, "type requirement");
+		static_assert(sqlpp::is_selectable_t<TF>::value, "type requirement");
 		static_assert(sqlpp::is_boolean_t<TT>::value, "type requirement");
 		static_assert(not sqlpp::is_numeric_t<TT>::value, "type requirement");
 		static_assert(not sqlpp::is_text_t<TT>::value, "type requirement");
@@ -69,15 +69,15 @@ int main()
 		using TI = decltype(t.alpha.in(sqlpp::value_list(std::vector<int>({1, 2, 3}))));
 		using TF = decltype(f.omega.in(sqlpp::value_list(std::vector<float>({1.0, 2.0, 3.0}))));
 		using TT = decltype(t.beta.in(sqlpp::value_list(std::vector<std::string>({"a", "b", "c"}))));
-		static_assert(sqlpp::is_named_expression_t<TI>::value, "type requirement");
+		static_assert(sqlpp::is_selectable_t<TI>::value, "type requirement");
 		static_assert(sqlpp::is_boolean_t<TI>::value, "type requirement");
 		static_assert(not sqlpp::is_numeric_t<TI>::value, "type requirement");
 		static_assert(not sqlpp::is_text_t<TI>::value, "type requirement");
-		static_assert(sqlpp::is_named_expression_t<TF>::value, "type requirement");
+		static_assert(sqlpp::is_selectable_t<TF>::value, "type requirement");
 		static_assert(sqlpp::is_boolean_t<TF>::value, "type requirement");
 		static_assert(not sqlpp::is_numeric_t<TF>::value, "type requirement");
 		static_assert(not sqlpp::is_text_t<TF>::value, "type requirement");
-		static_assert(sqlpp::is_named_expression_t<TF>::value, "type requirement");
+		static_assert(sqlpp::is_selectable_t<TF>::value, "type requirement");
 		static_assert(sqlpp::is_boolean_t<TT>::value, "type requirement");
 		static_assert(not sqlpp::is_numeric_t<TT>::value, "type requirement");
 		static_assert(not sqlpp::is_text_t<TT>::value, "type requirement");
@@ -88,15 +88,15 @@ int main()
 		using TI = decltype(t.alpha.not_in(1, 2, 3));
 		using TF = decltype(f.omega.not_in(1.0, 2.0, 3.0));
 		using TT = decltype(t.beta.not_in("a", "b", "c"));
-		static_assert(sqlpp::is_named_expression_t<TI>::value, "type requirement");
+		static_assert(sqlpp::is_selectable_t<TI>::value, "type requirement");
 		static_assert(sqlpp::is_boolean_t<TI>::value, "type requirement");
 		static_assert(not sqlpp::is_numeric_t<TI>::value, "type requirement");
 		static_assert(not sqlpp::is_text_t<TI>::value, "type requirement");
-		static_assert(sqlpp::is_named_expression_t<TF>::value, "type requirement");
+		static_assert(sqlpp::is_selectable_t<TF>::value, "type requirement");
 		static_assert(sqlpp::is_boolean_t<TF>::value, "type requirement");
 		static_assert(not sqlpp::is_numeric_t<TF>::value, "type requirement");
 		static_assert(not sqlpp::is_text_t<TF>::value, "type requirement");
-		static_assert(sqlpp::is_named_expression_t<TT>::value, "type requirement");
+		static_assert(sqlpp::is_selectable_t<TT>::value, "type requirement");
 		static_assert(sqlpp::is_boolean_t<TT>::value, "type requirement");
 		static_assert(not sqlpp::is_numeric_t<TT>::value, "type requirement");
 		static_assert(not sqlpp::is_text_t<TT>::value, "type requirement");
@@ -107,15 +107,15 @@ int main()
 		using TI = decltype(t.alpha.not_in(sqlpp::value_list(std::vector<int>({1, 2, 3}))));
 		using TF = decltype(f.omega.not_in(sqlpp::value_list(std::vector<float>({1.0, 2.0, 3.0}))));
 		using TT = decltype(t.beta.not_in(sqlpp::value_list(std::vector<std::string>({"a", "b", "c"}))));
-		static_assert(sqlpp::is_named_expression_t<TI>::value, "type requirement");
+		static_assert(sqlpp::is_selectable_t<TI>::value, "type requirement");
 		static_assert(sqlpp::is_boolean_t<TI>::value, "type requirement");
 		static_assert(not sqlpp::is_numeric_t<TI>::value, "type requirement");
 		static_assert(not sqlpp::is_text_t<TI>::value, "type requirement");
-		static_assert(sqlpp::is_named_expression_t<TF>::value, "type requirement");
+		static_assert(sqlpp::is_selectable_t<TF>::value, "type requirement");
 		static_assert(sqlpp::is_boolean_t<TF>::value, "type requirement");
 		static_assert(not sqlpp::is_numeric_t<TF>::value, "type requirement");
 		static_assert(not sqlpp::is_text_t<TF>::value, "type requirement");
-		static_assert(sqlpp::is_named_expression_t<TF>::value, "type requirement");
+		static_assert(sqlpp::is_selectable_t<TF>::value, "type requirement");
 		static_assert(sqlpp::is_boolean_t<TT>::value, "type requirement");
 		static_assert(not sqlpp::is_numeric_t<TT>::value, "type requirement");
 		static_assert(not sqlpp::is_text_t<TT>::value, "type requirement");
@@ -124,7 +124,7 @@ int main()
 	// Test like
 	{
 		using TT = decltype(t.beta.like("%c%"));
-		static_assert(sqlpp::is_named_expression_t<TT>::value, "type requirement");
+		static_assert(sqlpp::is_selectable_t<TT>::value, "type requirement");
 		static_assert(sqlpp::is_boolean_t<TT>::value, "type requirement");
 		static_assert(not sqlpp::is_numeric_t<TT>::value, "type requirement");
 		static_assert(not sqlpp::is_text_t<TT>::value, "type requirement");
@@ -141,15 +141,15 @@ int main()
 		static_assert(std::is_same<TI, TTI>::value, "type requirement");
 		static_assert(std::is_same<TF, TTF>::value, "type requirement");
 		static_assert(std::is_same<TT, TTT>::value, "type requirement");
-		static_assert(sqlpp::is_named_expression_t<TI>::value, "type requirement");
+		static_assert(sqlpp::is_selectable_t<TI>::value, "type requirement");
 		static_assert(sqlpp::is_boolean_t<TI>::value, "type requirement");
 		static_assert(not sqlpp::is_numeric_t<TI>::value, "type requirement");
 		static_assert(not sqlpp::is_text_t<TI>::value, "type requirement");
-		static_assert(sqlpp::is_named_expression_t<TF>::value, "type requirement");
+		static_assert(sqlpp::is_selectable_t<TF>::value, "type requirement");
 		static_assert(sqlpp::is_boolean_t<TF>::value, "type requirement");
 		static_assert(not sqlpp::is_numeric_t<TF>::value, "type requirement");
 		static_assert(not sqlpp::is_text_t<TF>::value, "type requirement");
-		static_assert(sqlpp::is_named_expression_t<TT>::value, "type requirement");
+		static_assert(sqlpp::is_selectable_t<TT>::value, "type requirement");
 		static_assert(sqlpp::is_boolean_t<TT>::value, "type requirement");
 		static_assert(not sqlpp::is_numeric_t<TT>::value, "type requirement");
 		static_assert(not sqlpp::is_text_t<TT>::value, "type requirement");
@@ -166,15 +166,15 @@ int main()
 		static_assert(std::is_same<TI, TTI>::value, "type requirement");
 		static_assert(std::is_same<TF, TTF>::value, "type requirement");
 		static_assert(std::is_same<TT, TTT>::value, "type requirement");
-		static_assert(sqlpp::is_named_expression_t<TI>::value, "type requirement");
+		static_assert(sqlpp::is_selectable_t<TI>::value, "type requirement");
 		static_assert(sqlpp::is_boolean_t<TI>::value, "type requirement");
 		static_assert(not sqlpp::is_numeric_t<TI>::value, "type requirement");
 		static_assert(not sqlpp::is_text_t<TI>::value, "type requirement");
-		static_assert(sqlpp::is_named_expression_t<TF>::value, "type requirement");
+		static_assert(sqlpp::is_selectable_t<TF>::value, "type requirement");
 		static_assert(sqlpp::is_boolean_t<TF>::value, "type requirement");
 		static_assert(not sqlpp::is_numeric_t<TF>::value, "type requirement");
 		static_assert(not sqlpp::is_text_t<TF>::value, "type requirement");
-		static_assert(sqlpp::is_named_expression_t<TT>::value, "type requirement");
+		static_assert(sqlpp::is_selectable_t<TT>::value, "type requirement");
 		static_assert(sqlpp::is_boolean_t<TT>::value, "type requirement");
 		static_assert(not sqlpp::is_numeric_t<TT>::value, "type requirement");
 		static_assert(not sqlpp::is_text_t<TT>::value, "type requirement");
@@ -187,11 +187,11 @@ int main()
 	{
 		using TI = decltype(exists(select(t.alpha).from(t)));
 		using TT = decltype(exists(select(t.beta).from(t)));
-		static_assert(sqlpp::is_named_expression_t<TI>::value, "type requirement");
+		static_assert(sqlpp::is_selectable_t<TI>::value, "type requirement");
 		static_assert(sqlpp::is_boolean_t<TI>::value, "type requirement");
 		static_assert(not sqlpp::is_numeric_t<TI>::value, "type requirement");
 		static_assert(not sqlpp::is_text_t<TI>::value, "type requirement");
-		static_assert(sqlpp::is_named_expression_t<TT>::value, "type requirement");
+		static_assert(sqlpp::is_selectable_t<TT>::value, "type requirement");
 		static_assert(sqlpp::is_boolean_t<TT>::value, "type requirement");
 		static_assert(not sqlpp::is_numeric_t<TT>::value, "type requirement");
 		static_assert(not sqlpp::is_text_t<TT>::value, "type requirement");
@@ -206,17 +206,17 @@ int main()
 		using TI = decltype(any(select(t.alpha).from(t)));
 		using TT = decltype(any(select(t.beta).from(t)));
 		using TF = decltype(any(select(f.omega).from(f)));
-		static_assert(not sqlpp::is_named_expression_t<TI>::value, "type requirement");
+		static_assert(not sqlpp::is_selectable_t<TI>::value, "type requirement");
 		static_assert(sqlpp::is_multi_expression_t<TI>::value, "type requirement");
 		static_assert(sqlpp::is_numeric_t<TI>::value, "type requirement");
 		static_assert(sqlpp::is_integral_t<TI>::value, "type requirement");
 		static_assert(not sqlpp::is_text_t<TI>::value, "type requirement");
-		static_assert(not sqlpp::is_named_expression_t<TF>::value, "type requirement");
+		static_assert(not sqlpp::is_selectable_t<TF>::value, "type requirement");
 		static_assert(sqlpp::is_multi_expression_t<TF>::value, "type requirement");
 		static_assert(sqlpp::is_numeric_t<TF>::value, "tFpe requirement");
 		static_assert(sqlpp::is_floating_point_t<TF>::value, "type requirement");
 		static_assert(not sqlpp::is_text_t<TF>::value, "type requirement");
-		static_assert(not sqlpp::is_named_expression_t<TT>::value, "type requirement");
+		static_assert(not sqlpp::is_selectable_t<TT>::value, "type requirement");
 		static_assert(sqlpp::is_multi_expression_t<TT>::value, "type requirement");
 		static_assert(not sqlpp::is_numeric_t<TT>::value, "type requirement");
 		static_assert(not sqlpp::is_integral_t<TT>::value, "type requirement");
@@ -229,18 +229,18 @@ int main()
 		using TI = decltype(some(select(t.alpha).from(t)));
 		using TT = decltype(some(select(t.beta).from(t)));
 		using TF = decltype(some(select(f.omega).from(f)));
-		static_assert(not sqlpp::is_named_expression_t<TI>::value, "type requirement");
+		static_assert(not sqlpp::is_selectable_t<TI>::value, "type requirement");
 		static_assert(sqlpp::is_multi_expression_t<TI>::value, "type requirement");
 		static_assert(sqlpp::is_numeric_t<TI>::value, "type requirement");
 		static_assert(sqlpp::is_integral_t<TI>::value, "type requirement");
 		static_assert(not sqlpp::is_text_t<TI>::value, "type requirement");
 		static_assert(sqlpp::is_numeric_t<TF>::value, "type requirement");
-		static_assert(not sqlpp::is_named_expression_t<TF>::value, "type requirement");
+		static_assert(not sqlpp::is_selectable_t<TF>::value, "type requirement");
 		static_assert(sqlpp::is_multi_expression_t<TF>::value, "type requirement");
 		static_assert(sqlpp::is_floating_point_t<TF>::value, "type requirement");
 		static_assert(not sqlpp::is_text_t<TF>::value, "type requirement");
 		static_assert(not sqlpp::is_numeric_t<TT>::value, "type requirement");
-		static_assert(not sqlpp::is_named_expression_t<TT>::value, "type requirement");
+		static_assert(not sqlpp::is_selectable_t<TT>::value, "type requirement");
 		static_assert(sqlpp::is_multi_expression_t<TT>::value, "type requirement");
 		static_assert(not sqlpp::is_integral_t<TT>::value, "type requirement");
 		static_assert(not sqlpp::is_floating_point_t<TT>::value, "type requirement");
@@ -254,11 +254,11 @@ int main()
 	{
 		using TI = decltype(avg(t.alpha));
 		using TF = decltype(avg(f.omega));
-		static_assert(sqlpp::is_named_expression_t<TI>::value, "type requirement");
+		static_assert(sqlpp::is_selectable_t<TI>::value, "type requirement");
 		static_assert(sqlpp::is_numeric_t<TI>::value, "type requirement");
 		static_assert(not sqlpp::is_integral_t<TI>::value, "type requirement");
 		static_assert(sqlpp::is_floating_point_t<TI>::value, "type requirement");
-		static_assert(sqlpp::is_named_expression_t<TF>::value, "type requirement");
+		static_assert(sqlpp::is_selectable_t<TF>::value, "type requirement");
 		static_assert(sqlpp::is_numeric_t<TF>::value, "type requirement");
 		static_assert(not sqlpp::is_integral_t<TF>::value, "type requirement");
 		static_assert(sqlpp::is_floating_point_t<TF>::value, "type requirement");
@@ -269,15 +269,15 @@ int main()
 		using TI = decltype(count(t.alpha));
 		using TT = decltype(count(t.beta));
 		using TF = decltype(count(f.omega));
-		static_assert(sqlpp::is_named_expression_t<TI>::value, "type requirement");
+		static_assert(sqlpp::is_selectable_t<TI>::value, "type requirement");
 		static_assert(sqlpp::is_numeric_t<TI>::value, "type requirement");
 		static_assert(sqlpp::is_integral_t<TI>::value, "type requirement");
 		static_assert(not sqlpp::is_floating_point_t<TI>::value, "type requirement");
-		static_assert(sqlpp::is_named_expression_t<TF>::value, "type requirement");
+		static_assert(sqlpp::is_selectable_t<TF>::value, "type requirement");
 		static_assert(sqlpp::is_numeric_t<TF>::value, "type requirement");
 		static_assert(sqlpp::is_integral_t<TF>::value, "type requirement");
 		static_assert(not sqlpp::is_floating_point_t<TF>::value, "type requirement");
-		static_assert(sqlpp::is_named_expression_t<TT>::value, "type requirement");
+		static_assert(sqlpp::is_selectable_t<TT>::value, "type requirement");
 		static_assert(sqlpp::is_numeric_t<TT>::value, "type requirement");
 		static_assert(sqlpp::is_integral_t<TT>::value, "type requirement");
 		static_assert(not sqlpp::is_floating_point_t<TT>::value, "type requirement");
@@ -288,15 +288,15 @@ int main()
 		using TI = decltype(max(t.alpha));
 		using TF = decltype(max(f.omega));
 		using TT = decltype(max(t.beta));
-		static_assert(sqlpp::is_named_expression_t<TI>::value, "type requirement");
+		static_assert(sqlpp::is_selectable_t<TI>::value, "type requirement");
 		static_assert(sqlpp::is_numeric_t<TI>::value, "type requirement");
 		static_assert(sqlpp::is_integral_t<TI>::value, "type requirement");
 		static_assert(not sqlpp::is_floating_point_t<TI>::value, "type requirement");
-		static_assert(sqlpp::is_named_expression_t<TF>::value, "type requirement");
+		static_assert(sqlpp::is_selectable_t<TF>::value, "type requirement");
 		static_assert(sqlpp::is_numeric_t<TF>::value, "type requirement");
 		static_assert(not sqlpp::is_integral_t<TF>::value, "type requirement");
 		static_assert(sqlpp::is_floating_point_t<TF>::value, "type requirement");
-		static_assert(sqlpp::is_named_expression_t<TT>::value, "type requirement");
+		static_assert(sqlpp::is_selectable_t<TT>::value, "type requirement");
 		static_assert(not sqlpp::is_numeric_t<TT>::value, "type requirement");
 		static_assert(sqlpp::is_text_t<TT>::value, "type requirement");
 	}
@@ -306,15 +306,15 @@ int main()
 		using TI = decltype(min(t.alpha));
 		using TF = decltype(min(f.omega));
 		using TT = decltype(min(t.beta));
-		static_assert(sqlpp::is_named_expression_t<TI>::value, "type requirement");
+		static_assert(sqlpp::is_selectable_t<TI>::value, "type requirement");
 		static_assert(sqlpp::is_numeric_t<TI>::value, "type requirement");
 		static_assert(sqlpp::is_integral_t<TI>::value, "type requirement");
 		static_assert(not sqlpp::is_floating_point_t<TI>::value, "type requirement");
-		static_assert(sqlpp::is_named_expression_t<TF>::value, "type requirement");
+		static_assert(sqlpp::is_selectable_t<TF>::value, "type requirement");
 		static_assert(sqlpp::is_numeric_t<TF>::value, "type requirement");
 		static_assert(not sqlpp::is_integral_t<TF>::value, "type requirement");
 		static_assert(sqlpp::is_floating_point_t<TF>::value, "type requirement");
-		static_assert(sqlpp::is_named_expression_t<TT>::value, "type requirement");
+		static_assert(sqlpp::is_selectable_t<TT>::value, "type requirement");
 		static_assert(not sqlpp::is_numeric_t<TT>::value, "type requirement");
 		static_assert(sqlpp::is_text_t<TT>::value, "type requirement");
 	}
@@ -323,11 +323,11 @@ int main()
 	{
 		using TI = decltype(sum(t.alpha));
 		using TF = decltype(sum(f.omega));
-		static_assert(sqlpp::is_named_expression_t<TF>::value, "type requirement");
+		static_assert(sqlpp::is_selectable_t<TF>::value, "type requirement");
 		static_assert(sqlpp::is_numeric_t<TI>::value, "type requirement");
 		static_assert(sqlpp::is_integral_t<TI>::value, "type requirement");
 		static_assert(not sqlpp::is_floating_point_t<TI>::value, "type requirement");
-		static_assert(sqlpp::is_named_expression_t<TF>::value, "type requirement");
+		static_assert(sqlpp::is_selectable_t<TF>::value, "type requirement");
 		static_assert(sqlpp::is_numeric_t<TF>::value, "type requirement");
 		static_assert(not sqlpp::is_integral_t<TF>::value, "type requirement");
 		static_assert(sqlpp::is_floating_point_t<TF>::value, "type requirement");
@@ -342,13 +342,13 @@ int main()
 		using TI = decltype(sqlpp::value(7));
 		using TF = decltype(sqlpp::value(1.5));
 		using TT = decltype(sqlpp::value("cheesecake"));
-		static_assert(not sqlpp::is_named_expression_t<TB>::value, "type requirement");
+		static_assert(not sqlpp::is_selectable_t<TB>::value, "type requirement");
 		static_assert(sqlpp::is_boolean_t<TB>::value, "type requirement");
-		static_assert(not sqlpp::is_named_expression_t<TB>::value, "type requirement");
+		static_assert(not sqlpp::is_selectable_t<TB>::value, "type requirement");
 		static_assert(sqlpp::is_integral_t<TI>::value, "type requirement");
-		static_assert(not sqlpp::is_named_expression_t<TI>::value, "type requirement");
+		static_assert(not sqlpp::is_selectable_t<TI>::value, "type requirement");
 		static_assert(sqlpp::is_floating_point_t<TF>::value, "type requirement");
-		static_assert(not sqlpp::is_named_expression_t<TT>::value, "type requirement");
+		static_assert(not sqlpp::is_selectable_t<TT>::value, "type requirement");
 		static_assert(sqlpp::is_text_t<TT>::value, "type requirement");
 	}
 
@@ -358,13 +358,13 @@ int main()
 		using TI = decltype(flatten(t.alpha, db));
 		using TF = decltype(flatten(f.omega, db));
 		using TT = decltype(flatten(t.beta, db));
-		static_assert(not sqlpp::is_named_expression_t<TB>::value, "type requirement");
+		static_assert(not sqlpp::is_selectable_t<TB>::value, "type requirement");
 		static_assert(sqlpp::is_boolean_t<TB>::value, "type requirement");
-		static_assert(not sqlpp::is_named_expression_t<TB>::value, "type requirement");
+		static_assert(not sqlpp::is_selectable_t<TB>::value, "type requirement");
 		static_assert(sqlpp::is_integral_t<TI>::value, "type requirement");
-		static_assert(not sqlpp::is_named_expression_t<TI>::value, "type requirement");
+		static_assert(not sqlpp::is_selectable_t<TI>::value, "type requirement");
 		static_assert(sqlpp::is_floating_point_t<TF>::value, "type requirement");
-		static_assert(not sqlpp::is_named_expression_t<TT>::value, "type requirement");
+		static_assert(not sqlpp::is_selectable_t<TT>::value, "type requirement");
 		static_assert(sqlpp::is_text_t<TT>::value, "type requirement");
 	}
 
@@ -382,13 +382,13 @@ int main()
 		static_assert(std::is_same<TI, TIN>::value, "type_requirement");
 		static_assert(std::is_same<TF, TFN>::value, "type_requirement");
 		static_assert(std::is_same<TT, TTN>::value, "type_requirement");
-		static_assert(not sqlpp::is_named_expression_t<TB>::value, "type requirement");
+		static_assert(not sqlpp::is_selectable_t<TB>::value, "type requirement");
 		static_assert(sqlpp::is_boolean_t<TB>::value, "type requirement");
-		static_assert(not sqlpp::is_named_expression_t<TB>::value, "type requirement");
+		static_assert(not sqlpp::is_selectable_t<TB>::value, "type requirement");
 		static_assert(sqlpp::is_integral_t<TI>::value, "type requirement");
-		static_assert(not sqlpp::is_named_expression_t<TI>::value, "type requirement");
+		static_assert(not sqlpp::is_selectable_t<TI>::value, "type requirement");
 		static_assert(sqlpp::is_floating_point_t<TF>::value, "type requirement");
-		static_assert(not sqlpp::is_named_expression_t<TT>::value, "type requirement");
+		static_assert(not sqlpp::is_selectable_t<TT>::value, "type requirement");
 		static_assert(sqlpp::is_text_t<TT>::value, "type requirement");
 	}
 
@@ -398,20 +398,20 @@ int main()
 		using TI = decltype(sqlpp::verbatim<sqlpp::bigint>("42"));
 		using TF = decltype(sqlpp::verbatim<sqlpp::floating_point>("1.5"));
 		using TT = decltype(sqlpp::verbatim<sqlpp::text>("cheesecake"));
-		static_assert(not sqlpp::is_named_expression_t<TB>::value, "type requirement");
+		static_assert(not sqlpp::is_selectable_t<TB>::value, "type requirement");
 		static_assert(sqlpp::is_boolean_t<TB>::value, "type requirement");
-		static_assert(not sqlpp::is_named_expression_t<TB>::value, "type requirement");
+		static_assert(not sqlpp::is_selectable_t<TB>::value, "type requirement");
 		static_assert(sqlpp::is_integral_t<TI>::value, "type requirement");
-		static_assert(not sqlpp::is_named_expression_t<TI>::value, "type requirement");
+		static_assert(not sqlpp::is_selectable_t<TI>::value, "type requirement");
 		static_assert(sqlpp::is_floating_point_t<TF>::value, "type requirement");
-		static_assert(not sqlpp::is_named_expression_t<TT>::value, "type requirement");
+		static_assert(not sqlpp::is_selectable_t<TT>::value, "type requirement");
 		static_assert(sqlpp::is_text_t<TT>::value, "type requirement");
 	}
 
 	// test verbatim_table
 	{
 		using T = decltype(sqlpp::verbatim_table("cheesecake"));
-		static_assert(not sqlpp::is_named_expression_t<T>::value, "type requirement");
+		static_assert(not sqlpp::is_selectable_t<T>::value, "type requirement");
 		static_assert(not sqlpp::is_expression_t<T>::value, "type requirement");
 		static_assert(sqlpp::is_table_t<T>::value, "type requirement");
 	}
@@ -419,7 +419,7 @@ int main()
 	// test verbatim_table alias
 	{
 		using T = decltype(sqlpp::verbatim_table("cheesecake").as(kaesekuchen));
-		static_assert(not sqlpp::is_named_expression_t<T>::value, "type requirement");
+		static_assert(not sqlpp::is_selectable_t<T>::value, "type requirement");
 		static_assert(not sqlpp::is_expression_t<T>::value, "type requirement");
 		static_assert(sqlpp::is_table_t<T>::value, "type requirement");
 		static_assert(sqlpp::is_alias_t<T>::value, "type requirement");

tests/InterpretTest.cpp

@@ -179,6 +179,9 @@ int main()
 	printer.reset();
 	std::cerr << serialize(x, printer).str() << std::endl;
 
+	printer.reset();
+	std::cerr << serialize(select(all_of(t)).from(t).where(t.alpha.in(select(f.epsilon).from(f).where(true))), printer).str() << std::endl;
+
 
 
 	return 0;

tests/MockDb.h

@@ -41,6 +41,12 @@ struct MockDbT: public sqlpp::connection
 	{
 		std::ostringstream _os;
 
+		_serializer_context_t() = default;
+		_serializer_context_t(const _serializer_context_t& rhs)	
+		{
+			_os << rhs._os.str();
+		}
+
 		std::string str() const
 		{
 			return _os.str();
@@ -159,8 +165,6 @@ struct MockDbT: public sqlpp::connection
 	template<typename PreparedInsert>
 		size_t run_prepared_insert(const PreparedInsert& x)
 		{
-			_serializer_context_t context;
-			::sqlpp::serialize(x, context);
 			return 0;
 		}
 
@@ -175,8 +179,6 @@ struct MockDbT: public sqlpp::connection
 	template<typename PreparedSelect>
 		result_t run_prepared_select(PreparedSelect& x)
 		{
-			_serializer_context_t context;
-			::sqlpp::serialize(x, context);
 			return {};
 		}
 

tests/PreparedTest.cpp

@@ -81,9 +81,9 @@ int main()
 		using Exp = decltype((t.beta.like(parameter(t.beta)) and t.alpha == parameter(t.alpha)) or t.gamma != parameter(t.gamma));
 		using T = sqlpp::make_parameter_list_t<Exp>;
 		T npl;
-		static_assert(std::is_same<typename sqlpp::value_type_of<decltype(t.alpha)>::_parameter_t, decltype(npl.alpha)>::value, "type requirement");
-		static_assert(std::is_same<typename sqlpp::value_type_of<decltype(t.beta)>::_parameter_t, decltype(npl.beta)>::value, "type requirement");
-		static_assert(std::is_same<typename sqlpp::value_type_of<decltype(t.gamma)>::_parameter_t, decltype(npl.gamma)>::value, "type requirement");
+		static_assert(std::is_same<sqlpp::parameter_value_t<sqlpp::value_type_of<decltype(t.alpha)>>, decltype(npl.alpha)>::value, "type requirement");
+		static_assert(std::is_same<sqlpp::parameter_value_t<sqlpp::value_type_of<decltype(t.beta)>>, decltype(npl.beta)>::value, "type requirement");
+		static_assert(std::is_same<sqlpp::parameter_value_t<sqlpp::value_type_of<decltype(t.gamma)>>, decltype(npl.gamma)>::value, "type requirement");
 	}
 
 	// Wonderful, now take a look at the parameter list of a select
@@ -96,9 +96,9 @@ int main()
 		using T = sqlpp::make_parameter_list_t<S>;
 		T npl;
 
-		static_assert(std::is_same<typename sqlpp::value_type_of<decltype(t.alpha)>::_parameter_t, decltype(npl.alpha)>::value, "type requirement");
-		static_assert(std::is_same<typename sqlpp::value_type_of<decltype(t.beta)>::_parameter_t, decltype(npl.beta)>::value, "type requirement");
-		static_assert(std::is_same<typename sqlpp::value_type_of<decltype(t.gamma)>::_parameter_t, decltype(npl.gamma)>::value, "type requirement");
+		static_assert(std::is_same<sqlpp::parameter_value_t<sqlpp::value_type_of<decltype(t.alpha)>>, decltype(npl.alpha)>::value, "type requirement");
+		static_assert(std::is_same<sqlpp::parameter_value_t<sqlpp::value_type_of<decltype(t.beta)>>, decltype(npl.beta)>::value, "type requirement");
+		static_assert(std::is_same<sqlpp::parameter_value_t<sqlpp::value_type_of<decltype(t.gamma)>>, decltype(npl.gamma)>::value, "type requirement");
 		npl.alpha = 7;
 		auto x = npl;
 		x = npl;

tests/ResultTest.cpp

@@ -43,7 +43,7 @@ int main()
 	static_assert(not sqlpp::null_is_trivial_value_t<decltype(t.alpha)>::value, "t.alpha does not say null_is_trivial");
 
 	// Using a non-enforcing db
-	for (const auto& row : db(select(all_of(t)).from(t).where(true)))
+	for (const auto& row : db(select(all_of(t), t.beta.like("")).from(t).where(true)))
 	{
 		static_assert(sqlpp::can_be_null_t<decltype(row.alpha)>::value, "row.alpha can be null");
 		static_assert(sqlpp::null_is_trivial_value_t<decltype(row.alpha)>::value, "row.alpha interprets null_is_trivial");