Re: Conditional NOT NULL constraint

On Wednesday 28 February 2007, Richard Huxton wrote:
> Andreas Joseph Krogh wrote:
> > Hi all!
> > Is there a simple way to add a "NOT NULL constraint" to a column without
> > using a trigger if another column is not null?
> > Something like this:
> >
> > CREATE TABLE activity(
> > id SERIAL primary key,
> > name varchar not null,
> > created timestamp not null default now(),
> > modified timestamp,
> > created_by integer not null,
> > modified_by integer
> > );
> >
> > alter table activity alter column modified_by set not null where modified
> > is not null;
> >
> > I want a constraint which says: "modified_by not null if modified is not
> > null".
>
> Would a CHECK do? Something like:
>
> ALTER TABLE activity ADD CONSTRAINT both_modified_set CHECK
> ((modified_by IS NULL AND modified IS NULL) OR (modified_by IS NOT NULL
> AND modified IS NOT NULL))

Certainly, thanks.

--
Andreas Joseph Krogh <andreak(at)officenet(dot)no>
Senior Software Developer / Manager
gpg public_key: http://dev.officenet.no/~andreak/public_key.asc
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