Re: Foreign superkey support
From: Kenneth Downs <knode.wants.this_at_see.sigblock>
Date: Wed, 09 Aug 2006 08:02:18 -0400
Message-Id: <tfvoq3-hv4.ln1_at_pluto.downsfam.net>
Date: Wed, 09 Aug 2006 08:02:18 -0400
Message-Id: <tfvoq3-hv4.ln1_at_pluto.downsfam.net>
Marshall wrote:
>
For example,
> we often speak of a foreign key constraint as belonging to
> one particular table, but it is equally a constraint on two tables.
> On one table it restricts inserts and on another table it restricts
> deletes. So we must necessarily classify it as a database
> constraint. But really, all constraints are all database constraints,
> although there may be some database constraints that only
> happen to be quantified over a single relvar.
>
I tend to visualize a foreign key as a pipe, it defines a meaningful transfer of data from one table to another.
-- Kenneth Downs Secure Data Software, Inc. (Ken)nneth_at_(Sec)ure(Dat)a(.com)Received on Wed Aug 09 2006 - 14:02:18 CEST