Re: Check constraint

On Wed, 17 Mar 2004, Richard Huxton wrote:

> On Wednesday 17 March 2004 12:03, Francisco Reyes 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.

Actually, shouldn't a table level check constraint be able to do this with
something like:
check (purchase_type!=3 or comment is not null)