Tim Keitt wrote: > I am combining query results that I know are disjoint. I'm wondering > how much overhead there is in calling union versus union all. (Just > curious really; I can't see a reason not to use union all.) UNION needs to uniquify the output, for which it plasters an additional sort step, whereas UNION ALL does not need to uniquify its output and thus it can avoid the sort step. Using UNION ALL is recommended wherever possible. -- Alvaro Herrera http://www.CommandPrompt.com/ The PostgreSQL Company - Command Prompt, Inc. -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
