Re: Another view on analysis and ER

From: David Cressey <cressey73_at_verizon.net>
Date: Thu, 06 Dec 2007 15:39:28 GMT
Message-ID: <QIU5j.8226$gs.3294_at_trndny08>


"Jon Heggland" <jon.heggland_at_ntnu.no> wrote in message news:fj909f$div$1_at_orkan.itea.ntnu.no...
> Quoth Bob Badour:
> > Jon Heggland wrote:
> >> Minor point: Is designation of primary keys really at the logical
level?
> >
> > Yes.
> >
> >> Are there any substantial logical consequences?
> >
> > The preponderance of foreign key references will refer to the primary
> > key when one designates a primary key.
>
> Granted, but it will be explicit which key a foreign key refers to (or
> it will be implicitly given by the attribute names in the foreign key).
> Primary key designation is neither necessary nor sufficient for this.

"So often times it happens that we live our lives in chains And we never even know we have the key "

The Eagles (Already Gone). Received on Thu Dec 06 2007 - 16:39:28 CET

Original text of this message