* Ben <bench@silentmedia.com> [2004-10-06 08:23:11 -0700]:
> If I have have the table:
>
> create table foo
> (
> a int references bar(id),
> b int references baz(id)
> )
>
> ... how do I make sure one and only one of the columns a and b are
> non-null? Is it even reasonable?
ALTER TABLE foo ADD CONSTRAINT must_have_a_or_b CHECK (a::int IS NULL
AND b::int IS NOT NULL OR a::int IS NOT NULL AND b::int IS NULL);
--
Steven Klassen - Lead Programmer
Command Prompt, Inc. - http://www.commandprompt.com/
PostgreSQL Replication & Support Services, (503) 667-4564
