- some expression fixup:

- the '.c.' attribute on a selectable now gets an
entry for every column expression in its columns
clause; previously, "unnamed" columns like functions
and CASE statements weren't getting put there.  Now
they will, using their full string representation
if no 'name' is available.
- The anonymous 'label' generated for otherwise
unlabeled functions and expressions now propagates
outwards at compile time for expressions like
select([select([func.foo()])])
- a CompositeSelect, i.e. any union(), union_all(),
intersect(), etc. now asserts that each selectable
contains the same number of columns.  This conforms
to the corresponding SQL requirement.
- building on the above ideas, CompositeSelects
now build up their ".c." collection based on
the names present in the first selectable only;
corresponding_column() now works fully for all
embedded selectables.

1 files changed, 2 insertions, 2 deletions

diff --git a/lib/sqlalchemy/sql/compiler.py b/lib/sqlalchemy/sql/compiler.py
index 8f2e3372a..666a38d39 100644
--- a/lib/sqlalchemy/sql/compiler.py
+++ b/lib/sqlalchemy/sql/compiler.py
@@ -464,7 +464,7 @@ class DefaultCompiler(engine.Compiled):
             not isinstance(column.table, sql.Select):
             return column.label(column.name)
         elif not isinstance(column, (sql._UnaryExpression, sql._TextClause)) and (not hasattr(column, 'name') or isinstance(column, sql._Function)):
-            return column.label(None)
+            return column.anon_label
         else:
             return column
 
@@ -728,7 +728,7 @@ class DefaultCompiler(engine.Compiled):
         return "RELEASE SAVEPOINT %s" % self.preparer.format_savepoint(savepoint_stmt)
     
     def __str__(self):
-        return self.string
+        return self.string or ''
 
 class DDLBase(engine.SchemaIterator):
     def find_alterables(self, tables):