"Richard Broersma" <richard.broersma@gmail.com> writes:
> On Sun, Aug 10, 2008 at 1:15 AM, <rafal@zorro.isa-geek.com> 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
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