From: Albert REINER <areiner@tph.tuwien.ac.at>
To: 'pgsql-sql@hub.org' <pgsql-sql@hub.org>
Subject: Re: [SQL] comparing 2 tables. . .
Date: Fri, 24 Sep 1999 22:47:49 +0200
Message-ID: <19990924224748.A182@frithjof> (raw)
In-Reply-To: <Pine.LNX.4.10.9909241525440.26357-100000@bsmlx17>
References: <01BF06A4.7FFF3C60@Dan>
<Pine.LNX.4.10.9909241525440.26357-100000@bsmlx17>
On Fri, Sep 24, 1999 at 03:32:51PM +0100, Stuart Rison wrote:
...
> Try:
>
> SELECT tab1.pkey FROM <your_table> tab1 WHERE tab1.pkey NOT IN (SELECT
> tab2.pkey FROM <your_other_table> tab2.pkey);
>
> or else (faster):
>
> SELECT tab1.pkey FROM <your_table> tab1 WHERE NOT EXISTS (SELECT 1 FROM
> <your_other_table> tab2 WHERE tab1.pkey=tab2.pkey);
Maybe this is trivial, but...
Is there a simple way to see that/why the last query is faster?
Albert.
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Cc: areiner@tph.tuwien.ac.at, pgsql-sql@hub.org
Subject: Re: [SQL] comparing 2 tables. . .
In-Reply-To: <19990924224748.A182@frithjof>
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