Re: Built in Functions use with recordsets

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Gordan Bobic" <gordan(at)freeuk(dot)com>
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: Built in Functions use with recordsets
Date: 2000-11-30 15:39:21
Message-ID: 4854.975598761@sss.pgh.pa.us
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"Gordan Bobic" <gordan(at)freeuk(dot)com> writes:
> over a certain set of records. In effect, I want to do something like:

> SELECT somefield
> FROM sometable
> WHERE otherfield = 'criteria'
> ORDER BY thirdfield
> LIMIT 10

> and then do an avg(somefield).

> Can this be done without using temp tables, in a single query?

Not if the order by/limit are essential to selecting the rows you need
to average over. At least not in 7.0 ... in 7.1 this'll work:

SELECT avg(somefield) FROM
(SELECT somefield FROM sometable ... LIMIT 10) t1;

For the moment a temp table is the way to go.

regards, tom lane

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