"Richard Broersma" <richard.broersma@xxxxxxxxx> writes: > On Sun, Aug 10, 2008 at 1:15 AM, <rafal@xxxxxxxxxxxxxxxxxx> wrote: > >> Since table TWO has a unique constraint on column ID, the (ID, OFONE) pair >> will also be unique, obviously. > > This statement is not completely true. The only part of the pair that > is true is ID. Also there is not unique constraint on the pare. So > there is no way to PG to build a foreing key on the pair. Uhm, afaics he's right. if ID is unique not null then <ID, OFONE> also has to be unique. That is, there could be duplicate values of OFONE but they'll all have different values of ID anyways. I'm not sure if there's a fundamental reason why there has to be an index that exactly matches the foreign key or not -- offhand I can't think of one. -- Gregory Stark EnterpriseDB http://www.enterprisedb.com Get trained by Bruce Momjian - ask me about EnterpriseDB's PostgreSQL training!
