Re: Triggers | rules for column updates

From: "A(dot) Kretschmer" <andreas(dot)kretschmer(at)schollglas(dot)com>
To: pgsql-novice(at)postgresql(dot)org
Subject: Re: Triggers | rules for column updates
Date: 2008-03-03 14:16:26
Message-ID: 20080303141624.GJ22441@a-kretschmer.de
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am Mon, dem 03.03.2008, um 15:47:58 +0200 mailte Szentpali Janos folgendes:
> Hi!
>
> I want to prevent any changes to a tuple if a field of the tuple has a
> certain value. Let's say I have a table with column col_1, col_2, col_3.
> I want to create something that will prevent updating col_2 and col_3 if
> and only if col_1 is say "1".
> Can I use a rule to do that. Can I somehow detect in a trigger function

I think, a RULE isn't the solution, but you can use a BEFORE UPDATE -
Trigger to check if OLD.col_1 = 1 and, in this case, RAISE an error.

Andreas
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Andreas Kretschmer
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