cross-table unique constraint

On Tue, Jan 06, 2004 at 07:10:28 +0000,
Randall Smith <randall@tnr.cc> wrote:

Is it possible to create a unique constraint on multiple fields in
related tables?

Not with the normal UNIQUE constraint. That will do multiple columns in
one table, but won't span tables.

You can probably do what you want using triggers.

So how might I go about doing this.

3 tables: a, b, and c

When these 3 tables are joined, there is a combination of 3 fields, one
field from each table, that should be unique.

Should there be a trigger that checks this condition on inserts/updates
on each of these tables?

Randall

Bruno Wolff III wrote: