Re: Views for denomalizing

On Thu, 3 Feb 2005 23:18:29 -0500, "Alan" <not.me_at_rcn.com> wrote:

>Normalization occurs at a logical level (note I did not say "the" logical
>level

Why not?

>, as I am just distinguishing logical from physical, not getting into
>logical vs conceptual- IOW, let's say logical and conceptual are the same
>thing

But they are very different.

>Views are a physical construction

Very very wrong!

Views are as logical as the rest of the relation variables.

It seems that you are calling physical model to the logical model and logical model to the conceptual model. This is a very common confusion in the literature.

This also explains your confusion between the conceptual and logical levels.

> and have nothing to do
>with normalization.

I disagree. View values are relations like any other relation. We can check whether a view is in a given normal form, but it does not mean that we should normalize the views.

>attributes
>[apply FDs to get to the next level, revealing PKs in the process]:
>relations (entities and relationships - an ERD is often created here)
>[apply transformation rules* to the ERD to get to the next level]
>-----boundry between logical and physical----------

An ERD is a conceptual design, and if you apply "transformation rules" to the ERD what you get is an incomplete logical design.

> Remember, a view is
>nothing but a stored SQL statement

A view is defined using a query statement, but a view is a relation or table variable.

Regards Received on Fri Feb 04 2005 - 15:00:37 CET