- Friendlier exception messages for unbound, implicit execution

- Implicit binding failures now raise UnboundExecutionError

1 files changed, 7 insertions, 1 deletions

diff --git a/lib/sqlalchemy/sql/expression.py b/lib/sqlalchemy/sql/expression.py
index 2e5797b34..ee867a2f9 100644
--- a/lib/sqlalchemy/sql/expression.py
+++ b/lib/sqlalchemy/sql/expression.py
@@ -1002,7 +1002,13 @@ class ClauseElement(object):
 
         e = self.bind
         if e is None:
-            raise exceptions.InvalidRequestError("This Compiled object is not bound to any Engine or Connection.")
+            label = getattr(self, 'description', self.__class__.__name__)
+            msg = ('This %s is not bound to an Engine or Connection.  '
+                   'Execution can not proceed without a database to execute '
+                   'against.  Either execute with an explicit connection or '
+                   'bind the MetaData of the underlying tables to enable '
+                   'implicit execution.') % label
+            raise exceptions.UnboundExecutionError(msg)
         return e.execute_clauseelement(self, multiparams, params)
 
     def scalar(self, *multiparams, **params):