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diff --git a/libodb/odb/query.hxx b/libodb/odb/query.hxx
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+// file      : odb/query.hxx
+// license   : GNU GPL v2; see accompanying LICENSE file
+
+#ifndef ODB_QUERY_HXX
+#define ODB_QUERY_HXX
+
+#include <odb/pre.hxx>
+
+#include <odb/forward.hxx>
+#include <odb/traits.hxx>
+
+namespace odb
+{
+  // Table alias for type T and tag Tag.
+  //
+  // The alias_traits interface consists of two things: the table_name
+  // static variable containing the name and, in case of a derived type
+  // in a polymorphic hierarchy, the base_traits typedef. Note that the
+  // same interface is exposed by object_traits, which is used when
+  // we need straight tables instead of aliases.
+  //
+  //
+  template <typename T, database_id DB, typename Tag>
+  struct alias_traits;
+
+  template <typename T, database_id DB>
+  struct query_columns_base;
+
+  template <typename T, database_id DB, typename A>
+  struct query_columns;
+
+  template <typename T, database_id DB, typename A>
+  struct pointer_query_columns;
+
+  // Object pointer syntax wrapper.
+  //
+  template <typename T>
+  struct query_pointer
+  {
+    query_pointer ()
+    {
+      // For some reason GCC needs this dummy c-tor if we make a static
+      // data member of this type const.
+    }
+
+    T*
+    operator-> () const
+    {
+      return 0; // All members in T are static.
+    }
+  };
+
+  // Query parameter decay traits.
+  //
+  template <typename T>
+  struct decay_traits
+  {
+    typedef const T& type;
+
+    static type
+    instance ();
+  };
+
+  template <typename T, std::size_t N>
+  struct decay_traits<T[N]>
+  {
+    typedef const T* type;
+
+    // Use the pointer comparability as a proxy for data comparability.
+    // Note that it is stricter than using element comparability (i.e.,
+    // one can compare int to char but not int* to char*).
+    //
+    static type
+    instance ();
+  };
+
+  // VC9 cannot handle certain cases of non-type arguments with default
+  // values in template functions (e.g., database::query()). As a result,
+  // we have to use the impl trick below instead of simply having kind
+  // as a second template argument with a default value.
+  //
+  template <typename T, database_id DB, class_kind kind>
+  struct query_selector_impl;
+
+  template <typename T, database_id DB>
+  struct query_selector_impl<T, DB, class_object>
+  {
+    typedef typename object_traits_impl<T, DB>::query_base_type base_type;
+
+    typedef
+    query_columns<T, DB, access::object_traits_impl<T, DB> >
+    columns_type;
+  };
+
+  template <typename T, database_id DB>
+  struct query_selector_impl<T, DB, class_view>
+  {
+    typedef typename view_traits_impl<T, DB>::query_base_type base_type;
+    typedef typename view_traits_impl<T, DB>::query_columns columns_type;
+  };
+
+  template <typename T, database_id DB>
+  struct query_selector: query_selector_impl<T, DB, class_traits<T>::kind>
+  {
+  };
+
+  template <typename T,
+            typename B = typename query_selector<T, id_common>::base_type>
+  class query;
+
+  namespace core
+  {
+    using odb::query;
+  }
+}
+
+#include <odb/post.hxx>
+
+#endif // ODB_QUERY_HXX