Re: SQL Question

From: Mo Holkar <pgsql(at)digitalmindgames(dot)com>
To: pgsql-novice(at)postgresql(dot)org
Subject: Re: SQL Question
Date: 2001-11-11 13:18:14
Message-ID: 5.1.0.14.2.20011111120039.009fda50@pop.ntlworld.com
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At 18:26 10/11/01, you wrote:
>A SQL Question...
>
>Bear with me... I'm kinda new here.
>
>I am trying to query table1, selecting records that do NOT have a relation
>in a subset from table3 that is related to table2.
>
>
>Example:
>
>table1(Trick table)
> 1_id,trickName,trickDescription
>
>table2(Magician table)
> 2_id,lastName,firstName
>
>table3(Trick-Magician-Knows table)
> 2_id,1_id
>
>if I choose some magician I want a list of tricks he/she DOES-NOT know.

Interesting question! I'm no SQL expert either... I would use something like:

SELECT one_id FROM table1 EXCEPT SELECT one_id FROM table3 WHERE
table3.two_id = table2.two_id AND table2.lastName = '<name of magician to
test for>';

which does generate the correct results, but there are probably more
elegant ways of doing it.

best,

Mo

Mo Holkar
Digital Mind Games -- log on to take over
mo(dot)holkar(at)digitalmindgames(dot)com
http://www.digitalmindgames.com

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