Re: automatic time/user stamp - rule or trigger?

On Wed, 5 Feb 2003, Jan Wieck wrote:

> Achilleus Mantzios wrote:
> >
> > On Wed, 5 Feb 2003, Neal Lindsay wrote:
> >
> > > I have a table that I want to keep track of the user who last modified
> > > it and the timestamp of the modification. Should I use a trigger or a rule?
> > >
> > > CREATE TABLE stampedtable (
> > > stampedtableid SERIAL PRIMARY KEY,
> > > updatestamp timestamp NOT NULL DEFAULT now(),
> > > updateuser name NOT NULL DEFAULT current_user,
> > > sometext text
> > > );
> > >
> > > I suspect that I want a rule, but all the examples in the documentation
> > > seem to update a separate table and not override (or add) the
> > > insert/update to the timestamp and name columns.
> >
> > You may want to use rules if you need rewriting.
> > What you actually need is some sort of driver to a specific table.
> > You could create a view to that table (to hide the accounting columns),
> > and then create rules on that view that do the job as you wish.
>
> I'm sure you want to use a BEFORE INSERT OR UPDATE trigger that modifies
> NEW.updatestamp in place just before the row get's written.
>
> A rule will not work here because rules cannot cause the same action on
> the same table they are called for.

Thats why the view comes in place.

>
>
> Jan
>
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==================================================================
Achilleus Mantzios
S/W Engineer
IT dept
Dynacom Tankers Mngmt
Nikis 4, Glyfada
Athens 16610
Greece
tel: +30-10-8981112
fax: +30-10-8981877
email: achill(at)matrix(dot)gatewaynet(dot)com
mantzios(at)softlab(dot)ece(dot)ntua(dot)gr