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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
In-reply-to: <5444D5FF.5070407@enercoop.org>
References: <544339CA.5090202@enercoop.org>
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Comments: In-reply-to Laurent Martelli <laurent.martelli@enercoop.org>
 message dated "Mon, 20 Oct 2014 11:29:35 +0200"
Date: Mon, 20 Oct 2014 09:58:08 -0400
Message-ID: <3181.1413813488@sss.pgh.pa.us>
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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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