From: Tom Lane <tgl@sss.pgh.pa.us>
To: Laurent Martelli <laurent.martelli@enercoop.org>
Cc: pgsql-performance@postgresql.org
Subject: Re: IS NOT NULL and LEFT JOIN
Date: Mon, 20 Oct 2014 09:58:08 -0400
Message-ID: <3181.1413813488@sss.pgh.pa.us> (raw)
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Laurent Martelli <laurent.martelli@enercoop.org> writes:
> Do we agree that both queries are identical ?
No, they *aren't* identical. Go consult any SQL reference. Left join
conditions don't work the way you seem to be thinking: after the join,
the RHS column might be null, rather than equal to the LHS column.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, laurent.martelli@enercoop.org
Subject: Re: IS NOT NULL and LEFT JOIN
In-Reply-To: <3181.1413813488@sss.pgh.pa.us>
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