Re: multi column foreign key for implicitly unique columns - Mailing list pgsql-sql

Tom Lane wrote:
> Jan Wieck <JanWieck@Yahoo.com> writes:
> 
>>However, Bruce, this should be on the TODO list:
>>     * Allow foreign key to reference a superset of the columns
>>       covered by a unique constraint on the referenced table.
> 
> 
> See the followup discussion as to why this is a bad idea.

Maybe an alternative todo?

* Allow multiple unique constraints to share an index where one is a 
superset of the others' columns.

That way you can mark it unique without having the overhead of multiple 
indexes.

--   Richard Huxton  Archonet Ltd