Re: Foreign superkey support

Jon Heggland wrote:
> Are there any DMBSs apart from Dataphor that support foreign superkeys
> without undue hassle? SQL systems support them in that a superkey may be
> declared UNIQUE, and thus referred to by a foreign key, but I'm looking
> for more explicit support.
>
> Or more generally, are there any DBMSs that support inclusion
> dependencies (apart from the special case of foreign keys, naturally)
> directly?
>
> Or for that matter, how widespread is multi-relvar constraint support
> (apart from foreign keys)? As far as I know, neither Oracle nor MSSQL
> support SQL ASSERTIONs. Are there any DMBSs that do?

It occurs to me a superkey reference implies something less than 3rd normal form because any attributes over and above the irreducible key will be functionally dependent on the foreign key.

Why include them in the referencing relation at all? Received on Tue Aug 08 2006 - 03:47:06 CEST