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Re: ORDER BY <field not in return list>

From: mark(at)mark(dot)mielke(dot)cc
To: "Marc G(dot) Fournier" <scrappy(at)postgresql(dot)org>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: ORDER BY <field not in return list>
Date: 2005-07-25 22:54:38
Message-ID: 20050725225438.GA20944@mark.mielke.cc (view raw or flat)
Thread:
Lists: pgsql-hackers
On Mon, Jul 25, 2005 at 06:11:08PM -0300, Marc G. Fournier wrote:
> Just curious as to whether or not a warning or something should be issued 
> in a case like:
>   SELECT c.*
>     FROM company c, company_summary cs
>    WHERE c.id = cs.id
>      AND cs.detail = 'test'
> ORDER BY cs.fullname;

> Unless I'm missing something, the ORDER BY clause has no effect, but an 
> EXPLAIN shows it does take extra time, obviously ...

Why would it have no effect? If there is a one to many mapping between
fullname and id, and if the rows in c with the same fullname have
different rows in c.*, then it does matter.

For the casual observer, only seeing the output of the table, they would
see a consistent reporting order, but would be unable to derive how the
table rows were sorted. :-)

mark

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