From: Mark Fenbers <Mark.Fenbers@noaa.gov>
To: pgsql-sql@postgresql.org
Subject: sub-selects
Date: Mon, 16 May 2005 15:45:43 -0400
Message-ID: <4288F867.8090600@noaa.gov> (raw)
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Is there a way to make a query more efficient by executing a sub-select
only once?<br>
<br>
In a query such as:<br>
<br>
<tt>SELECT a, (select b from c where d = e limit 1), npoints( (select b
from c where d = e limit 1) )<br>
FROM f<br>
WHERE isValid( (select b from c where d = e limit 1) );<br>
</tt><br>
I do the same sub-select 3 times in the query. I tried the following:<br>
<br>
<tt>SELECT a, (select b from c where d = e limit 1)<b> AS g</b>,
npoints( <b>g</b> )<br>
FROM f<br>
WHERE isValid( <b>g</b> );<br>
</tt><br>
But this gave an error regarding "column 'g' does not exist". How can
I avoid making the same sub-select 3 times? <br>
<br>
Mark<br>
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To: pgsql-sql@postgresql.org
Cc: Mark.Fenbers@noaa.gov
Subject: Re: sub-selects
In-Reply-To: <4288F867.8090600@noaa.gov>
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