From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | The Hermit Hacker <scrappy(at)hub(dot)org> |
Cc: | pgsql-sql(at)postgresql(dot)org, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: LEFT JOIN ... |
Date: | 2001-06-18 18:07:38 |
Message-ID: | 7462.992887658@sss.pgh.pa.us |
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Lists: | pgsql-hackers pgsql-sql |
The Hermit Hacker <scrappy(at)hub(dot)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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