Merge branch 'feature/case' into develop

include/sqlpp11/case.h

@@ -0,0 +1,189 @@
+/*
+ * Copyright (c) 2015-2015, 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_CASE_H
+#define SQLPP_CASE_H
+
+#include <sqlpp11/type_traits.h>
+#include <sqlpp11/char_sequence.h>
+#include <sqlpp11/data_types/boolean.h>
+#include <sqlpp11/detail/type_set.h>
+
+namespace sqlpp
+{
+  namespace detail
+  {
+    template <typename When>
+    using valid_when_t =
+        logic::all_t<is_boolean_t<wrap_operand_t<When>>::value, is_expression_t<wrap_operand_t<When>>::value>;
+
+    template <typename Then>
+    using valid_then_t = is_expression_t<wrap_operand_t<Then>>;
+
+    template <typename Then, typename Else>
+    using valid_else_t = logic::all_t<
+        is_expression_t<wrap_operand_t<Else>>::value,
+        logic::any_t<is_sql_null_t<Then>::value,
+                     is_sql_null_t<wrap_operand_t<Else>>::value,
+                     std::is_same<value_type_of<Then>, value_type_of<wrap_operand_t<Else>>>::value>::value>;
+  }
+
+  template <typename When, typename Then, typename Else>
+  struct case_t
+      : public expression_operators<
+            case_t<When, Then, Else>,
+            typename std::conditional<is_sql_null_t<Then>::value, value_type_of<Else>, value_type_of<Then>>::type>,
+        public alias_operators<case_t<When, Then, Else>>
+  {
+    using _traits = make_traits<value_type_of<Then>, tag::is_expression>;
+    using _nodes = detail::type_vector<When, Then, Else>;
+
+    case_t(When when, Then then, Else else_) : _when(when), _then(then), _else(else_)
+    {
+    }
+
+    case_t(const case_t&) = default;
+    case_t(case_t&&) = default;
+    case_t& operator=(const case_t&) = default;
+    case_t& operator=(case_t&&) = default;
+    ~case_t() = default;
+
+    When _when;
+    Then _then;
+    Else _else;
+  };
+
+  template <typename When, typename Then>
+  class case_then_t
+  {
+    template <typename Else>
+    auto _else_impl(const std::true_type&, Else else_) -> case_t<When, Then, Else>
+    {
+      return {_when, _then, else_};
+    }
+
+    template <typename Else>
+    auto _else_impl(const std::false_type&, Else else_) -> void;
+
+  public:
+    case_then_t(When when, Then then) : _when(when), _then(then)
+    {
+    }
+
+    case_then_t(const case_then_t&) = default;
+    case_then_t(case_then_t&&) = default;
+    case_then_t& operator=(const case_then_t&) = default;
+    case_then_t& operator=(case_then_t&&) = default;
+    ~case_then_t() = default;
+
+    template <typename Else>
+    auto else_(Else else_) -> decltype(this->_else_impl(detail::valid_else_t<Then, Else>{}, else_))
+    {
+      static_assert(detail::valid_else_t<Then, Else>::value,
+                    "arguments of then and else must be expressions of the same type (or null)");
+      return _else_impl(detail::valid_else_t<Then, Else>{}, else_);
+    }
+
+  private:
+    When _when;
+    Then _then;
+  };
+
+  template <typename When>
+  class case_when_t
+  {
+    template <typename Then>
+    auto _then_impl(const std::true_type&, Then t) -> case_then_t<When, wrap_operand_t<Then>>
+    {
+      return {_when, t};
+    }
+
+    template <typename Then>
+    auto _then_impl(const std::false_type&, Then t) -> void;
+
+  public:
+    case_when_t(When when) : _when(when)
+    {
+    }
+
+    case_when_t(const case_when_t&) = default;
+    case_when_t(case_when_t&&) = default;
+    case_when_t& operator=(const case_when_t&) = default;
+    case_when_t& operator=(case_when_t&&) = default;
+    ~case_when_t() = default;
+
+    template <typename Then>
+    auto then(Then t) -> decltype(this->_then_impl(detail::valid_then_t<Then>{}, t))
+    {
+      static_assert(detail::valid_then_t<Then>::value, "then argument must be a value expression");
+      return _then_impl(detail::valid_then_t<Then>{}, t);
+    }
+
+  private:
+    When _when;
+  };
+
+  template <typename Context, typename When, typename Then, typename Else>
+  struct serializer_t<Context, case_t<When, Then, Else>>
+  {
+    using _serialize_check = serialize_check_of<When, Then, Else>;
+    using T = case_t<When, Then, Else>;
+
+    static Context& _(const T& t, Context& context)
+    {
+      context << "(CASE WHEN ";
+      serialize(t._when, context);
+      context << " THEN ";
+      serialize(t._then, context);
+      context << " ELSE ";
+      serialize(t._else, context);
+      context << " END)";
+      return context;
+    }
+  };
+
+  namespace detail
+  {
+    template <typename When>
+    auto case_when_impl(const std::true_type&, When when) -> case_when_t<wrap_operand_t<When>>
+    {
+      return {when};
+    }
+
+    template <typename When>
+    auto case_when_impl(const std::false_type&, When when) -> void;
+  }
+
+  template <typename When>
+  auto case_when(When when) -> decltype(detail::case_when_impl(detail::valid_when_t<When>{}, when))
+  {
+    static_assert(detail::valid_when_t<When>::value, "case_when condition must be a boolean expression");
+
+    return detail::case_when_impl(detail::valid_when_t<When>{}, when);
+  }
+}
+
+#endif

include/sqlpp11/data_types.h

@@ -33,5 +33,6 @@
 #include <sqlpp11/data_types/text.h>
 #include <sqlpp11/data_types/day_point.h>
 #include <sqlpp11/data_types/time_point.h>
+#include <sqlpp11/data_types/no_value.h>
 
 #endif

include/sqlpp11/data_types/no_value.h

@@ -27,25 +27,12 @@
 #ifndef SQLPP_NO_VALUE_H
 #define SQLPP_NO_VALUE_H
 
-#include <type_traits>
-#include <sqlpp11/expression_operators.h>
-#include <sqlpp11/data_types/column_operators.h>
+#include <sqlpp11/data_types/no_value/data_type.h>
+#include <sqlpp11/data_types/no_value/operand.h>
+#include <sqlpp11/data_types/no_value/wrap_operand.h>
+#include <sqlpp11/data_types/no_value/expression_operators.h>
+#include <sqlpp11/data_types/no_value/column_operators.h>
+#include <sqlpp11/data_types/no_value/parameter_value.h>
+#include <sqlpp11/data_types/no_value/result_field.h>
 
-namespace sqlpp
-{
-  struct no_value_t
-  {
-    using _traits = make_traits<void>;
-  };
-
-  template <typename Base>
-  struct expression_operators<Base, no_value_t>
-  {
-  };
-
-  template <typename Base>
-  struct column_operators<Base, no_value_t>
-  {
-  };
-}
 #endif

include/sqlpp11/data_types/no_value/column_operators.h

@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2013-2015, 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_NO_VALUE_COLUMN_OPERATORS_H
+#define SQLPP_NO_VALUE_COLUMN_OPERATORS_H
+
+#include <sqlpp11/data_types/column_operators.h>
+
+namespace sqlpp
+{
+  struct no_value_t;
+
+  template <typename Base>
+  struct column_operators<Base, no_value_t>
+  {
+  };
+}
+#endif

include/sqlpp11/data_types/no_value/data_type.h

@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2013-2015, 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_NO_VALUE_DATA_TYPE_H
+#define SQLPP_NO_VALUE_DATA_TYPE_H
+
+#include <sqlpp11/type_traits.h>
+
+namespace sqlpp
+{
+  struct no_value_t
+  {
+    using _traits = make_traits<no_value_t>;
+    using _cpp_value_type = void;
+
+    template <typename T>
+    using _is_valid_operand = wrong_t<T>;
+  };
+}
+
+#endif

include/sqlpp11/data_types/no_value/expression_operators.h

@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2013-2015, 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_NO_VALUE_EXPRESSION_OPERATORS_H
+#define SQLPP_NO_VALUE_EXPRESSION_OPERATORS_H
+
+#include <sqlpp11/expression_return_types.h>
+#include <sqlpp11/expression_operators.h>
+#include <sqlpp11/basic_expression_operators.h>
+
+namespace sqlpp
+{
+  template <typename Expression>
+  struct expression_operators<Expression, no_value_t> : public basic_expression_operators<Expression, no_value_t>
+  {
+  };
+}
+
+#endif

include/sqlpp11/data_types/no_value/operand.h

@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2013-2015, 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_NO_VALUE_OPERAND_H
+#define SQLPP_NO_VALUE_OPERAND_H
+
+namespace sqlpp
+{
+  // There is no no_value operand
+}
+
+#endif

include/sqlpp11/data_types/no_value/parameter_value.h

@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2013-2015, 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_NO_VALUE_PARAMETER_VALUE_H
+#define SQLPP_NO_VALUE_PARAMETER_VALUE_H
+
+namespace sqlpp
+{
+  // There is no no_value parameter
+}
+
+#endif

include/sqlpp11/data_types/no_value/result_field.h

@@ -0,0 +1,72 @@
+/*
+ * Copyright (c) 2013-2015, 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_NO_VALUE_RESULT_FIELD_H
+#define SQLPP_NO_VALUE_RESULT_FIELD_H
+
+#include <sqlpp11/result_field.h>
+#include <sqlpp11/data_types/no_value/data_type.h>
+#include <sqlpp11/field_spec.h>
+
+namespace sqlpp
+{
+  template <typename Db, typename NameType, bool CanBeNull, bool NullIsTrivialValue>
+  struct result_field_t<Db, field_spec_t<NameType, no_value_t, CanBeNull, NullIsTrivialValue>>
+  {
+    template <typename Target>
+    void _bind(Target&, size_t)
+    {
+    }
+
+    template <typename Target>
+    void _post_bind(Target&, size_t)
+    {
+    }
+
+    void _validate() const
+    {
+    }
+
+    void _invalidate() const
+    {
+    }
+
+    constexpr bool is_null() const
+    {
+      return true;
+    }
+  };
+
+  template <typename Db, typename NameType, bool CanBeNull, bool NullIsTrivialValue>
+  inline std::ostream& operator<<(
+      std::ostream& os, const result_field_t<Db, field_spec_t<NameType, no_value_t, CanBeNull, NullIsTrivialValue>>&)
+  {
+    os << "NULL";
+    return os;
+  }
+}
+
+#endif

include/sqlpp11/data_types/no_value/wrap_operand.h

@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2013-2015, 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_NO_VALUE_WRAP_OPERAND_H
+#define SQLPP_NO_VALUE_WRAP_OPERAND_H
+
+namespace sqlpp
+{
+  // There is no no_value operand
+}
+
+#endif

include/sqlpp11/default_value.h

@@ -27,7 +27,7 @@
 #ifndef SQLPP_DEFAULT_VALUE_H
 #define SQLPP_DEFAULT_VALUE_H
 
-#include <sqlpp11/no_value.h>
+#include <sqlpp11/data_types/no_value.h>
 
 namespace sqlpp
 {

include/sqlpp11/functions.h

@@ -31,6 +31,7 @@
 #include <sqlpp11/parameter_list.h>
 #include <sqlpp11/data_types.h>
 #include <sqlpp11/aggregate_functions.h>
+#include <sqlpp11/case.h>
 #include <sqlpp11/in.h>
 #include <sqlpp11/not_in.h>
 #include <sqlpp11/is_null.h>

include/sqlpp11/into.h

@@ -29,7 +29,7 @@
 
 #include <sqlpp11/statement_fwd.h>
 #include <sqlpp11/type_traits.h>
-#include <sqlpp11/no_value.h>
+#include <sqlpp11/data_types/no_value.h>
 #include <sqlpp11/no_data.h>
 #include <sqlpp11/prepared_insert.h>
 #include <sqlpp11/serializer.h>

include/sqlpp11/multi_column.h

@@ -27,7 +27,6 @@
 #ifndef SQLPP_MULTI_COLUMN_H
 #define SQLPP_MULTI_COLUMN_H
 
-#include <sqlpp11/no_value.h>
 #include <sqlpp11/logic.h>
 #include <sqlpp11/detail/type_set.h>
 
@@ -35,6 +34,8 @@
 
 namespace sqlpp
 {
+  struct no_value_t;
+
   template <typename AliasProvider, typename... Columns>
   struct multi_column_alias_t;
 

include/sqlpp11/noop.h

@@ -28,7 +28,7 @@
 #define SQLPP_NOOP_H
 
 #include <type_traits>
-#include <sqlpp11/no_value.h>
+#include <sqlpp11/data_types/no_value.h>
 #include <sqlpp11/serializer.h>
 #include <sqlpp11/prepared_execute.h>
 

include/sqlpp11/null.h

@@ -27,7 +27,7 @@
 #ifndef SQLPP_NULL_H
 #define SQLPP_NULL_H
 
-#include <sqlpp11/no_value.h>
+#include <sqlpp11/data_types/no_value.h>
 
 namespace sqlpp
 {

include/sqlpp11/prepared_execute.h

@@ -29,7 +29,7 @@
 
 #include <sqlpp11/parameter_list.h>
 #include <sqlpp11/result.h>
-#include <sqlpp11/no_value.h>
+#include <sqlpp11/data_types/no_value.h>
 
 namespace sqlpp
 {

include/sqlpp11/prepared_insert.h

@@ -29,7 +29,7 @@
 
 #include <sqlpp11/parameter_list.h>
 #include <sqlpp11/result.h>
-#include <sqlpp11/no_value.h>
+#include <sqlpp11/data_types/no_value.h>
 
 namespace sqlpp
 {

include/sqlpp11/prepared_remove.h

@@ -29,7 +29,7 @@
 
 #include <sqlpp11/parameter_list.h>
 #include <sqlpp11/result.h>
-#include <sqlpp11/no_value.h>
+#include <sqlpp11/data_types/no_value.h>
 
 namespace sqlpp
 {

include/sqlpp11/prepared_select.h

@@ -29,7 +29,7 @@
 
 #include <sqlpp11/parameter_list.h>
 #include <sqlpp11/result.h>
-#include <sqlpp11/no_value.h>
+#include <sqlpp11/data_types/no_value.h>
 
 namespace sqlpp
 {

include/sqlpp11/prepared_update.h

@@ -29,7 +29,7 @@
 
 #include <sqlpp11/parameter_list.h>
 #include <sqlpp11/result.h>
-#include <sqlpp11/no_value.h>
+#include <sqlpp11/data_types/no_value.h>
 
 namespace sqlpp
 {

include/sqlpp11/select_column_list.h

@@ -30,7 +30,7 @@
 #include <tuple>
 #include <sqlpp11/result_row.h>
 #include <sqlpp11/table.h>
-#include <sqlpp11/no_value.h>
+#include <sqlpp11/data_types/no_value.h>
 #include <sqlpp11/field_spec.h>
 #include <sqlpp11/expression_fwd.h>
 #include <sqlpp11/select_pseudo_table.h>

include/sqlpp11/select_pseudo_table.h

@@ -27,7 +27,7 @@
 #ifndef SQLPP_SELECT_PSEUDO_TABLE_H
 #define SQLPP_SELECT_PSEUDO_TABLE_H
 
-#include <sqlpp11/no_value.h>
+#include <sqlpp11/data_types/no_value.h>
 
 namespace sqlpp
 {

include/sqlpp11/single_table.h

@@ -28,7 +28,7 @@
 #define SQLPP_SINGLE_TABLE_H
 
 #include <sqlpp11/type_traits.h>
-#include <sqlpp11/no_value.h>
+#include <sqlpp11/data_types/no_value.h>
 #include <sqlpp11/no_data.h>
 #include <sqlpp11/serializer.h>
 #include <sqlpp11/prepared_insert.h>

include/sqlpp11/table.h

@@ -33,7 +33,7 @@
 #include <sqlpp11/column.h>
 #include <sqlpp11/detail/type_set.h>
 #include <sqlpp11/join.h>
-#include <sqlpp11/no_value.h>
+#include <sqlpp11/data_types/no_value.h>
 
 namespace sqlpp
 {

include/sqlpp11/type_traits.h

@@ -38,12 +38,13 @@
 
 namespace sqlpp
 {
+  struct no_value_t;
   namespace detail
   {
     template <typename T, typename Enable = void>
     struct value_type_of_impl
     {
-      static_assert(wrong_t<value_type_of_impl>::value, "Attempting to obtain value type from type without value_type");
+      using type = no_value_t;
     };
 
     template <typename T>

include/sqlpp11/verbatim.h

@@ -27,7 +27,7 @@
 #ifndef SQLPP_VERBATIM_H
 #define SQLPP_VERBATIM_H
 
-#include <sqlpp11/no_value.h>
+#include <sqlpp11/data_types/no_value.h>
 #include <sqlpp11/type_traits.h>
 #include <sqlpp11/serialize.h>
 

include/sqlpp11/verbatim_table.h

@@ -27,7 +27,7 @@
 #ifndef SQLPP_VERBATIM_TABLE_H
 #define SQLPP_VERBATIM_TABLE_H
 
-#include <sqlpp11/no_value.h>
+#include <sqlpp11/data_types/no_value.h>
 
 namespace sqlpp
 {

tests/Interpret.cpp

@@ -216,5 +216,9 @@ int Interpret(int, char**)
   printer.reset();
   std::cerr << serialize(select(all_of(s)).from(s).where(true), printer).str() << std::endl;
 
+  printer.reset();
+  std::cerr << serialize(sqlpp::case_when(true).then(t.alpha).else_(t.alpha + 1).as(t.beta), printer).str()
+            << std::endl;
+
   return 0;
 }

tests/MockDb.h

@@ -29,7 +29,7 @@
 #include <sstream>
 #include <iostream>
 #include <sqlpp11/schema.h>
-#include <sqlpp11/no_value.h>
+#include <sqlpp11/data_types/no_value.h>
 #include <sqlpp11/serialize.h>
 #include <sqlpp11/serializer_context.h>
 #include <sqlpp11/connection.h>

tests/Select.cpp

@@ -164,5 +164,11 @@ int Select(int, char**)
 
   select(sqlpp::value(7).as(t.alpha));
 
+  for (const auto& row :
+       db(select(sqlpp::case_when(true).then(sqlpp::null).else_(sqlpp::null).as(t.beta)).from(t).where(true)))
+  {
+    std::cerr << row.beta << std::endl;
+  }
+
   return 0;
 }