Re: Normalization and DBMS

On Tue, 11 May 2004 18:25:19 -0300,
=?iso-8859-1?q?Leandro_Guimar=E3es_Faria_Corsetti_Dutra?= <leandro_at_dutra.fastmail.fm> wrote:

> 1NF was initially applied to clean our databases of such
>horrors as:
>
> CREATE TABLE
>(
> subject,
> year,
> grade_jan,
> grade_feb,
> ...
>)

Yes, but this table is in 1NF.

> These were known as repeating groups. Now there is a debate
>about nested tables which I haven't looked into properly.

I prefer: relation valued attributes :)

The conclusion is that they are useful in very rare circumstances.

For instance a good use could be:

var Keys real relation { RelVar Char, Attributes relation { AttributeName Char } } key { Id, Attributes }

> But I do
>maintain that getting rid of repeating groups is The Right Thing To
>Do, and one of the reasons why relational is so much better.

Yes, but relations with "repeating groups" are still relations thus they are in 1NF.

Regards
  Alfredo Received on Wed May 12 2004 - 10:50:43 CEST