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From: Richard Huxton <dev@archonet.com>
To: David Garamond <davidgaramond@gmail.com>
Cc: pgsql-sql <pgsql-sql@postgresql.org>
Subject: Re: autoupdating mtime column
Date: Fri, 04 Aug 2006 17:05:50 +0100
Message-ID: <44D3705E.9050304@archonet.com> (raw)
In-Reply-To: <7c33d060608040810j7f722af3g6a3185bf1cb990d6@mail.gmail.com>
References: <7c33d060608040516n799af906sf74e1c645a47caff@mail.gmail.com>
	<44D34242.6000901@archonet.com>
	<7c33d060608040810j7f722af3g6a3185bf1cb990d6@mail.gmail.com>

David Garamond wrote:
> On 8/4/06, Richard Huxton <dev@archonet.com> wrote:
>> David Garamond wrote:
>> > Dear all,
>> >
>> > Please see SQL below. I'm already satisfied with everything except I
>> > wish in
>> > #4, mtime got automatically updated to NOW() if not explicitly SET in
>> > UPDATE
>> > statement. Is there a way to make the mtime column behave more like I
>> > wanted? Thanks in advance.
>>
>> Just check for OLD.mtime = NEW.mtime, or am I missing something here?
> 
> How do I differentiate between:
> 
> UPDATE t SET mtime=mtime ...;
> 
> in which mtime is specifically set and should not change, and
> 
> UPDATE t SET foo=bar ...;
> 
> in which mtime is not mentioned and should be updated automagically to
> NOW().

You can't. The trigger knows nothing about the original statement, just 
the old and new tuple values.

You could use SET foo=DEFAULT, but that's neither more or less 
convenient than now() in my eyes.

-- 
   Richard Huxton
   Archonet Ltd




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