Re: How to ensure data consistency?
Date: Thu, 9 Sep 2004 12:07:32 +0200
Message-ID: <20040909120732.6c7b769a.felix.klee_at_inka.de>
On Wed, 08 Sep 2004 05:40:40 GMT Dan wrote:
> > If the DBMS supports deferred constraint mechanisms, I circular
> > Foreign Key constraint relationship will work. [snip]
>
> This won't work with multiple subtypes, either overlapping or
> disjoint; only mutual existence dependence relationships that are one
> to one. But triggers will do just fine. Front end enforcement is not
> always necessary.
Even in the case where the specialization types are mutually exclusive, I don't see how circular foreign key constraints can be utilized. What should the bipartite primary key in the main table reference if used as a foreign key?
Thus, using Joe Celko's solution, there still is the problem that the main table may contain entries for which there are no subtables.
Felix Received on Thu Sep 09 2004 - 12:07:32 CEST