X-Original-To: pgsql-sql@postgresql.org
Received: from spampd.localdomain (postgresql.org [64.49.215.8])
	by postgresql.org (Postfix) with ESMTP id DF105475AA9
	for <pgsql-sql@postgresql.org>; Sun,  6 Apr 2003 17:54:28 -0400 (EDT)
Received: from news.hub.org (news.hub.org [64.49.215.80])
	by postgresql.org (Postfix) with ESMTP id 405C2474E42
	for <pgsql-sql@postgresql.org>; Sun,  6 Apr 2003 17:54:25 -0400 (EDT)
Received: by news.hub.org (Postfix, from userid 8)
	id 24CA443A89E; Sun,  6 Apr 2003 17:54:25 -0400 (EDT)
From: saads@umich.edu (Saad Saeed)
X-Newsgroups: comp.databases.postgresql.sql
Subject: Creating a foreign key on the Union of two tables
Date: 6 Apr 2003 14:53:50 -0700
Organization: http://groups.google.com/
Lines: 9
Message-ID: <a811aba0.0304061353.664e2263@posting.google.com>
Content-Type: text/plain; charset=ISO-8859-1
X-Complaints-To: groups-abuse@google.com
To: pgsql-sql@postgresql.org
Content-Transfer-Encoding: quoted-printable
X-Spam-Status: No, hits=-1.6 required=5.0
	tests=BAYES_30
	version=2.50
X-Spam-Level: 
X-Spam-Checker-Version: SpamAssassin 2.50 (1.173-2003-02-20-exp)
X-Archive-Number: 200304/95
X-Sequence-Number: 12796

I have 2 tables "A" and "B" in mySQL. They both have an attribute 'id'
which is unique between the 2 tables. I want the union of these 2
attributes to be a foreign key in a 3rd table "C". How do I specify
this constraing in sql (mySQL) in table C? And for complex reasons I
cannot merge the 2 tables A and B.

Thanks,

-Saad