From: Tom Lane <tgl@sss.pgh.pa.us>
To: The Hermit Hacker <scrappy@hub.org>
Cc: pgsql-sql@postgresql.org
Cc: pgsql-hackers@postgresql.org
Subject: Re: LEFT JOIN ...
Date: Mon, 18 Jun 2001 14:07:38 -0400
Message-ID: <7462.992887658@sss.pgh.pa.us> (raw)
In-Reply-To: <Pine.BSF.4.33.0106181414511.22744-100000@mobile.hub.org>
References: <Pine.BSF.4.33.0106181414511.22744-100000@mobile.hub.org>
The Hermit Hacker <scrappy@hub.org> writes:
> FROM note_links nl, notes n LEFT JOIN calendar c ON (n.nid = c.nid)
> WHERE (n.type = 'A' OR n.type = 'N' OR n.type = 'H' OR n.type = 'C')
> AND (nl.id = 15748 AND contact_lvl = 'company')
> AND n.nid = nl.nid
> ORDER BY start DESC;
> Is there some way to write the above so that it evaluates:
> first, so that it only has to do the LEFT JOIN on the *one* n.nid that is
> returned, instead of the 86736 that are in the table?
Try adding ... AND n.nid = 15748 ... to the WHERE. It's not very
bright about making that sort of transitive-equality deduction for
itself...
regards, tom lane
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To: pgsql-sql@postgresql.org
Cc: tgl@sss.pgh.pa.us, scrappy@hub.org, pgsql-hackers@postgresql.org
Subject: Re: LEFT JOIN ...
In-Reply-To: <7462.992887658@sss.pgh.pa.us>
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