From: Mike Bayer <mike_mp@zzzcomputing.com>
Date: Wed, 12 Jan 2011 16:31:13 +0000 (-0500)
Subject: - add a note about query.order_by(None) with union etc.  clarifies [ticket:2022]
X-Git-Tag: rel_0_7b1~82
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=be4e6d4cd515dd91370a5944fa4dab70a8de206b;p=thirdparty%2Fsqlalchemy%2Fsqlalchemy.git

- add a note about query.order_by(None) with union etc.  clarifies [ticket:2022]
---

diff --git a/lib/sqlalchemy/orm/query.py b/lib/sqlalchemy/orm/query.py
index d5f0ef0ca5..5964459182 100644
--- a/lib/sqlalchemy/orm/query.py
+++ b/lib/sqlalchemy/orm/query.py
@@ -1073,7 +1073,14 @@ class Query(object):
 
             SELECT * FROM (SELECT * FROM X UNION SELECT * FROM y UNION 
                             SELECT * FROM Z)
-
+        
+        Note that many database backends do not allow ORDER BY to
+        be rendered on a query called within UNION, EXCEPT, etc.
+        To disable all ORDER BY clauses including those configured
+        on mappers, issue ``query.order_by(None)`` - the resulting
+        :class:`.Query` object will not render ORDER BY within 
+        its SELECT statement.
+        
         """