| From: | Bruno Wolff III <bruno(at)wolff(dot)to> |
|---|---|
| To: | sklassen(at)commandprompt(dot)com |
| Cc: | Ben <bench(at)silentmedia(dot)com>, Postgres general mailing list <pgsql-general(at)postgresql(dot)org> |
| Subject: | Re: database constraints |
| Date: | 2004-10-06 17:48:16 |
| Message-ID: | 20041006174816.GA18262@wolff.to |
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| Thread: | |
| Lists: | pgsql-general pgsql-hackers |
On Wed, Oct 06, 2004 at 08:35:21 -0700,
sklassen(at)commandprompt(dot)com wrote:
> * Ben <bench(at)silentmedia(dot)com> [2004-10-06 08:23:11 -0700]:
>
> 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);
A simpler constraint is:
check (a is null <> b is null);
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