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Re: Pizza Example

From: Anthony W. Youngman <wol_at_thewolery.demon.co.uk>
Date: Sat, 24 Apr 2004 15:21:48 +0100
Message-ID: <PvvEA2N8fniAFw4c@thewolery.demon.co.uk>


In message <408a6adc.400025_at_news.wanadoo.es>, Alfredo Novoa <alfredo_at_ncs.es> writes
>On Fri, 23 Apr 2004 14:41:27 -0400, "Laconic2" <laconic2_at_comcast.net>
>wrote:
>
>>The ER model was such a thing when I first started working with databases.
>>Most of the existing databases were built on the Network (CODASYL) model,
>>and many of the new databases were to be built on the relational model. It
>>turns out that, if you have a good ER model of the data requirements, this
>>"common model" can be turned into either a CODASYL model or a Relational
>>model, as you choose.
>
>But if you have an ER model you don't have a database design. The
>modeling capabilities of the ER model are very very poor and it leads
>to poor relational database designs.

If it's an easy transform from ER to relational, then ER cannot be poorer than the relational equivalent - indeed, it seems it is a richer design.
>
>You can not turn a relational database design in a ER model in almost
>all cases.
>

Yes it is a richer design, if you then can't go back the other way.
>
>Regards
> Alfredo

Cheers,
Wol

-- 
Anthony W. Youngman - wol at thewolery dot demon dot co dot uk
HEX wondered how much he should tell the Wizards. He felt it would not be a
good idea to burden them with too much input. Hex always thought of his reports
as Lies-to-People.
The Science of Discworld : (c) Terry Pratchett 1999
Received on Sat Apr 24 2004 - 09:21:48 CDT

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