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Re: Normalisation

From: Jon Heggland <heggland_at_idi.ntnu.no>
Date: Wed, 6 Jul 2005 10:32:38 +0200
Message-ID: <MPG.1d35b50c4b06ec539896e6@news.ntnu.no>


In article <q_Cye.138126$Kn.7314565_at_phobos.telenet-ops.be>, jan.hidders_at_REMOVETHIS.pandora.be says...
> > Yet you did say "Another option is to treat the field as a set-valued
> > field (since it apparently can contain 0 or 1 values) which
> > means that you are not in 1NF and should first normalize such that you
> > are."
>
> Good point. I'm making the silent assumption here that if you allow
> nested relations, then you probably also have the nest/unnest relations
> as are usually found in the nested relational algebra.

The quote didn't mention nested relations, it is about sets. Do you make that assumption about sets as well? Why? Why not about strings?

> If you don't have
> those then you are arguably treating it more as an atomic value than a
> set value.

So the presence of nest/unnest is the problem? For the sake of the argument, let us say that a relation with relation-valued attributes is in 1NF iff there are no nest/unnest operators.

Given the above definition, do you think that a relation with relationvalued  attributes in the presence of nest/unnest should be "normalised" to reach 1NF? Why?

(Btw, I'm not sure what you mean by "nested relational algebra"---Date's GROUP and UNGROUP don't affect the other operators in any way.)

-- 
Jon
Received on Wed Jul 06 2005 - 03:32:38 CDT

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