Re: [Q] Update from a table

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Ladislav Lenart <lenartlad(at)volny(dot)cz>
Cc: "pgsql-general(at)postgresql(dot)org" <pgsql-general(at)postgresql(dot)org>
Subject: Re: [Q] Update from a table
Date: 2013-12-05 14:14:24
Message-ID: 14196.1386252864@sss.pgh.pa.us
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Ladislav Lenart <lenartlad(at)volny(dot)cz> writes:
> What happens if I issue UPDATE SET FROM... but with incomplete/buggy WHERE
> condition and thus SEVERAL rows from the from_list match ONE row to update?

Any given row will be updated at most once. However, the from_list row
it gets updated against will be unpredictable, depending on the
implementation of the join.

regards, tom lane

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