Re: Entity vs. Table

From: Alfredo Novoa <alfredo_at_ncs.es>
Date: 14 Jun 2004 06:27:05 -0700
Message-ID: <e4330f45.0406140527.45b16719@posting.google.com>

"Alan" <alan_at_erols.com> wrote in message news:<2ittqgFqitf3U1_at_uni-berlin.de>...

> It's not a requirement, but it is a starting point. If you start with a 3NF
> physical model, you can denormalize for the sake of performance.

Physical designs can't be 3NF. Normalization only applies to the logical level.

> > A TRY :
> > Physical datamodel is a model of the
> > database implementation ? (The databasemodel).
> > (Can contain redundancy does not have to be like the
> > logical datamodel, but MUST implement the logical model).
>
> Yes and no. There should be no redundancy

Why not?

>, or it is not a propely
> implemented 3NF relational database. Otherwise, yes.

3NF has nothing to do with the physical level.

> A logical data model follows after the ERD, so I would say no to this part.

You can not represent many business rules with an ERD. IMO the ERD is something we should avoid.

> Yes, with one small change. An ERD is a conceptual business model of the
> data and the realtionships(associations) among the data.

It is very incomplete and often leads to bad designs.

Regards
Alfredo Received on Mon Jun 14 2004 - 08:27:05 CDT