Re: Composite Keys

Bruce Elrick wrote:
>
> I couldn't grok this out of the docs.  Does PostGreSQL support composite
> keys?  I am aware of the current lack of foreign key support except through
> refint.so and triggers.
>
> In my case, I'd like to have a single address table enforcing a unique
> (employeenum, addrtype) instead of a home_address, office_address, and
> worksite_address table, each enforcing a unique (employeenum) (which is a
> foreign key of the employee table).  In reading up on the unique constraint,
> it is not obvious (to someone who is not a DBA) whether the uniqueness is
> enforced on the combination of fields or on the fields separately.
>
> That is, (empnum, addrtype)'s of the form (A, x), (A, y), (B, x), (C, x), (C,
> z) are ok, where you see neither empnum nor addrtype are unique, only the
> composition is.
>
> I'm probably stating the obvious but I am unsure...
>

bad form to reply to one's own post...but I just saw
   CREATE TABLE films (
       code      CHAR(05),
       title     VARCHAR(40),
       did       DECIMAL(03),
       date_prod DATE,
       kind      CHAR(10),
       len       INTERVAL HOUR TO MINUTE,
       CONSTRAINT code_title PRIMARY KEY(code,title)
       );
(and two following) where I see that one can use a primary key _table_
constraint on multiple columns, thus giving composite keys....

Sorry for the wasted bandwidth...

On a related note, how close is foreign key support?  7.x?

Thanks....
Bruce
--
Bruce Elrick, Ph.D.                       Saltus Technology Consulting Group
Personal: belrick@home.com                          IBM Certified Specialist
Business: belrick@saltus.ab.ca          ADSM, AIX Support, RS/6000 SP, HACMP