Re: Trigger help - updates to column data with null values

NICE!!! Worked beautifully! I figured NULL's were not evaluating as a value,
but I didn't have the correct operators:

these constructs effectively act as though null were a normal data value,
> rather than “unknown”.

I guess I wasn't reading the right part of the manuals! LOL! Thanks so
much!

Greg Fischer
www.1stbyte.com

On Tue, Mar 2, 2010 at 8:07 PM, Craig Ringer <craig(at)postnewspapers(dot)com(dot)au>wrote:

> Greg Fischer wrote:
> > Hello all!
> > I do my best to read and google my way around issues, but I seem to be
> > missing something. Probably simple too.
> >
> > So I have a trigger function, in which I'd like to check if a particular
> > column has changed. It works great, unless either the OLD or NEW values
> > are NULL. The purpose is to create a audit/log of the record. I prefer
> > to only test for certain columns, not the whole table.
> >
> >
> > CREATE OR REPLACE FUNCTION tr_employees_bu()
> > RETURNS trigger AS
> > $BODY$
> > begin
> > if (new.trainingdate <> old.trainingdate) then
>
> Instead, try the test:
>
> new.trainingdate IS DISTINCT FROM old.trainingdate
>
> See the manual for 'IS DISTINCT FROM'.
>
> --
> Craig Ringer
>