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To: josh@agliodbs.com
Cc: "A.M." <agentm@cmu.edu>, pgsql-sql@postgresql.org
Subject: Re: UNION and ORDER BY ... IS NULL ASC 
In-reply-to: <200304041852.30121.josh@agliodbs.com> 
References: <1E4E6631-670A-11D7-89FA-0030657192DA@cmu.edu>
	<200304041852.30121.josh@agliodbs.com>
Comments: In-reply-to Josh Berkus <josh@agliodbs.com>
	message dated "Fri, 04 Apr 2003 18:52:30 -0800"
Date: Fri, 04 Apr 2003 23:17:40 -0500
Message-ID: <11805.1049516260@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>
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Josh Berkus <josh@agliodbs.com> writes:
>> ERROR:  ORDER BY on a UNION/INTERSECT/EXCEPT result must be on one of 
>> the result columns

> I do believe that this is per the SQL spec; UNIONs may only be sorted on the 
> output columns.

Right.  We extend the SQL spec for ORDER BY on simple selects, but we
have not gotten around to doing so for ORDER BY on set-operation
results.  You can only sort by unadorned output columns.

Patches to improve this are welcome ;-)

			regards, tom lane