From: chester c young <chestercyoung@yahoo.com>
To: nha <lyondif02@free.fr>
Cc: sql pgsql <pgsql-sql@postgresql.org>
Subject: Re: how to tell if column set on update
Date: Tue, 21 Jul 2009 20:51:11 -0700 (PDT)
Message-ID: <137458.25689.qm@web54304.mail.re2.yahoo.com> (raw)
> Le 20/07/09 15:19, chester c young a écrit :
> > within a trigger need to know if the UPDATE statement
> set a column. the column might be set to the old value
> or a different value.
> >
> > (want to make sure the app is sending all necessary
> values)
> >
> > thanks
> >
>
> If the column to test is known -- e.g. column MyCol --,
> NEW.MyCol and
> OLD.MyCol -- respectively value of MyCol after UPDATE and
> value of MyCol
> before UPDATE -- can be compared.
for example,
create table t1( c1 int, c2 int );
insert into t1 values( 1, 2 );
1) update t1 set c1=4 where c1=1;
2) update t1 set c1=4, c2=2 where c1=1;
each update results in the same row, but in the second update c2 was actually set.
a trigger on the update - how do we know if c2 has been actually set or not?
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To: pgsql-sql@postgresql.org
Cc: chestercyoung@yahoo.com, lyondif02@free.fr
Subject: Re: how to tell if column set on update
In-Reply-To: <137458.25689.qm@web54304.mail.re2.yahoo.com>
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