Re: Check constraint

On Wednesday 17 March 2004 17:30, Gregory Wood wrote:
> >>I have a "comment" field in a table that I want populated if another
> >> field has a certain value. Is it possible to set a check constraint for
> >> this?
> >>
> >>Example:
> >>Let's say we have fields
> >>Purchase_type smallint check(purchase_type <4)
> >>comment varchar
> >>
> >>I need a check rule to something like (pseudo code)
> >>check (if purchase_type = 3 then NOT NULL comment)
> >
> > No - you'll want a BEFORE UPDATE/INSERT trigger. It shouldn't be
> > difficult to do though.
>
> I don't see why not:
>
> CHECK ((purchase_type <> 3) OR ((purchase_type = 3) AND comment IS NOT
> NULL))

Ah - I misread the original post. I thought Francisco was trying to
automatically copy the comment field when purchase_type=3.

Apologies, Francisco

--
Richard Huxton
Archonet Ltd