Re: nested select query take too long

What about using an outer join instead? This requires PostgreSQL 7.1 or later.

SELECT DISTINCT dom_ns.domname, dom_ns.tldtype
FROM dom_ns LEFT OUTER JOIN domains ON dom_ns.domname = domains.domname
WHERE domain.domname IS NULL;

--Wes Sheldahl

"Arsalan Zaidi" <azaidi%directi(dot)com(at)interlock(dot)lexmark(dot)com> on 11/19/2001
05:31:43 AM

To: pgsql-general%postgresql(dot)org(at)interlock(dot)lexmark(dot)com
cc: (bcc: Wesley Sheldahl/Lex/Lexmark)
Subject: [GENERAL] nested select query take too long

Hi.

The following query takes absolutely *ages* to run. Even with just a 1000
records in each table. It seems to me that the nested query is being run for
*every* value in the dom_ns table.

SELECT DISTINCT dom_ns.domname, dom_ns.tldtype FROM dom_ns WHERE
dom_ns.domname NOT IN (SELECT domname FROM domains WHERE domname IS NOT
NULL);

Why should is this happening? I just want the nested query to run once!

Thanks in advance.

--Arsalan.

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People often hate those things which they do not know, or cannot understand.
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