Re: count(*), EXISTS, indexes

From: Itai Zukerman <zukerman(at)math-hat(dot)com>
To: pgsql-sql(at)postgresql(dot)org
Subject: Re: count(*), EXISTS, indexes
Date: 2003-04-11 21:32:00
Message-ID: 87smsora9b.fsf@matt.w80.math-hat.com
Views: Raw Message | Whole Thread | Download mbox | Resend email
Thread:
Lists: pgsql-sql

> CREATE TABLE A (x int PRIMARY KEY, real v);
> CREATE TABLE B (x int);
>
> I'd like to calculate:
>
> 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;

--
Itai Zukerman <http://www.math-hat.com/~zukerman/>

In response to

Responses

Browse pgsql-sql by date

  From Date Subject
Next Message Josh Berkus 2003-04-11 21:42:48 Re: count(*), EXISTS, indexes
Previous Message Itai Zukerman 2003-04-11 21:22:33 Re: count(*), EXISTS, indexes