From da0d47a805655b7398d832a72c2031cc13a93e02 Mon Sep 17 00:00:00 2001
From: rbock <rbock@eudoxos.de>
Date: Sun, 15 Feb 2015 16:06:14 +0100
Subject: [PATCH] Fixed conditions for using sub select as alias

---
 include/sqlpp11/select_column_list.h |  2 +-
 include/sqlpp11/statement.h          |  4 ++--
 include/sqlpp11/type_traits.h        | 15 +++++++++++++++
 3 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/include/sqlpp11/select_column_list.h b/include/sqlpp11/select_column_list.h
index 36e78c91..7fae3d2e 100644
--- a/include/sqlpp11/select_column_list.h
+++ b/include/sqlpp11/select_column_list.h
@@ -286,7 +286,7 @@ namespace sqlpp
 					template<typename AliasProvider>
 						_alias_t<AliasProvider> as(const AliasProvider& aliasProvider) const
 						{
-							run_check_t<_statement_t>::_();
+							consistency_check_t<_statement_t>::_();
 							static_assert(_statement_t::_can_be_used_as_table(), "statement cannot be used as table, e.g. due to missing tables");
 							static_assert(logic::none_t<is_multi_column_t<Columns>::value...>::value, "cannot use multi-columns in sub selects");
 							return _table_t<AliasProvider>(_get_statement()).as(aliasProvider);
diff --git a/include/sqlpp11/statement.h b/include/sqlpp11/statement.h
index 8fe803d7..209a62e0 100644
--- a/include/sqlpp11/statement.h
+++ b/include/sqlpp11/statement.h
@@ -130,12 +130,12 @@ namespace sqlpp
 
 				// A select can be used as a pseudo table if
 				//   - at least one column is selected
-				//   - the select is complete (leaks no tables)
+				//   - the select is complete (leaks no table requirements)
 				static constexpr bool _can_be_used_as_table()
 				{
 					return has_result_row_t<_statement_t>::value
 					 	and _required_tables::size::value == 0
-					 	and _required_ctes::size::value == 0
+					 	and _all_provided_ctes::size::value == 0 // a sub-select must not contain a WITH
 						? true
 						: false;
 				}
diff --git a/include/sqlpp11/type_traits.h b/include/sqlpp11/type_traits.h
index 630457a6..e6dc033f 100644
--- a/include/sqlpp11/type_traits.h
+++ b/include/sqlpp11/type_traits.h
@@ -296,6 +296,21 @@ namespace sqlpp
 			}
 	};
 
+	template<typename T, typename Enable = void>
+		struct consistency_check
+		{
+			using type = assert_run_statement_or_prepared_t;
+		};
+
+	template<typename T>
+		struct consistency_check<T, typename std::enable_if<is_statement_t<T>::value or is_prepared_statement_t<T>::value>::type>
+		{
+			using type = typename T::_consistency_check;
+		};
+
+	template<typename T>
+		using consistency_check_t = typename consistency_check<T>::type;
+
 	template<typename T, typename Enable = void>
 		struct run_check
 		{