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Re: MV Keys

From: Jon Heggland <heggland_at_idi.ntnu.no>
Date: Thu, 2 Mar 2006 14:48:48 +0100
Message-ID: <MPG.1e7116291a66271e989774@news.ntnu.no>


In article <1141261284.404545.215620_at_v46g2000cwv.googlegroups.com>, marshall.spight_at_gmail.com says...
> dawn wrote:
> > Although all NF's are defined as first requiring 1NF, at least with
> > Codd and his camps.
>
> Indirectly, insofar as for all N, normal form N subsumes the definition
> of normal form N-1. Again, is there any reason we should care?

Yes. This means that we can check to see if a relvar is in 5NF, and not need to check the lesser ones.

> > I agree with Date tossing out normalization as defined by Codd, but not
> > with his attempt to redefine 1NF to be meaningless. It is difficult to
> > move foward if people still have the mistaken impression that database
> > theory requires that we remove repeating groups.
>
> Repeating groups are still a bad idea, regardless of whether we
> allow nested relations or not. I don't agree that allowing
> nested relations means we're going to want to start using
> repeating groups.

How do you define "repeating group" as opposed to "nested relation", then? I assume "nested relation" and "relation-valued attribute" is the same thing.

-- 
Jon
Received on Thu Mar 02 2006 - 07:48:48 CST

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