| From: | Stephan Szabo <sszabo(at)megazone(dot)bigpanda(dot)com> |
|---|---|
| To: | Richard Huxton <dev(at)archonet(dot)com> |
| Cc: | Francisco Reyes <lists(at)natserv(dot)com>, pgsql General List <pgsql-general(at)postgresql(dot)org> |
| Subject: | Re: Check constraint |
| Date: | 2004-03-17 17:28:57 |
| Message-ID: | 20040317092711.D23707@megazone.bigpanda.com |
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| Thread: | |
| Lists: | pgsql-general |
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)
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