From: Itai Zukerman <zukerman@math-hat.com>
To: Stephan Szabo <sszabo@megazone23.bigpanda.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: count(*), EXISTS, indexes
Date: Fri, 11 Apr 2003 18:18:59 -0400
Message-ID: <8765pkr830.fsf@matt.w80.math-hat.com> (raw)
In-Reply-To: <20030411150926.C838-100000@megazone23.bigpanda.com>
References: <20030411150926.C838-100000@megazone23.bigpanda.com>
>> > CREATE TABLE A (x int PRIMARY KEY, real v);
>> > CREATE TABLE B (x int);
>> >
>> > SELECT sum(v) FROM A WHERE EXISTS (SELECT 1 FROM B WHERE A.x=B.x);
>>
>> This seems to be a reasonably-performing workaround:
>>
>> SELECT DISTINCT x INTO TEMP C FROM A,B WHERE A.x=B.x;
>> SELECT sum(v) FROM A,C WHERE A.x=C.x;
>
> Hmm, given that, would something like:
>
> select sum(v) from
> (select distinct on(x) x,v from a,b where a.x=b.x) as foo;
Excellent. Thanks!
--
Itai Zukerman <http://www.math-hat.com/~zukerman/;
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To: pgsql-sql@postgresql.org
Cc: zukerman@math-hat.com, sszabo@megazone23.bigpanda.com
Subject: Re: count(*), EXISTS, indexes
In-Reply-To: <8765pkr830.fsf@matt.w80.math-hat.com>
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