Re: Few confusing things about first normal form

From: <Srubys_at_gmail.com>
Date: Thu, 23 Oct 2008 11:20:20 -0700 (PDT)
Message-ID: <a032f30b-1b11-47a3-8d6f-d9c2e403d69f_at_79g2000hsk.googlegroups.com>


greetings

> If ITEM truly is multi-valued then ORDER is not a relation. All
> attributes are equally important. The fact that it has a regular
> scalar attribute as a key is irrelevant because if ITEM isn't one
> value then the operators like equality, assignment and projection
> can't apply in their usual sense.
> I don't mean to exclude the possibility of relation-valued attributes.
> A relation is a value so RVA's are perfectly OK in principle.

What do you mean by relation-valued attribute? Regular attribute in relational table?

> I don't mean to exclude the possibility of relation-valued attributes.
> A relation is a value so RVA's are perfectly OK in principle.

I donít quite understand what your arguments here

> Formally speaking any relation is *always* in 1NF by definition. A table
> (for instance in SQL) is said to be in 1NF if it accurately represents some
> relation, ie. it has: no duplicate rows; unique column names; no nulls; at
> least one key.

But table can also be declared without the key? Wouldnít that mean that table isnít in 1NF?

Anyways, I realize SQL doesnít allow multi-valued attributes, but I figured at least in theory they would be allowed, since I canít bring myself to believe that the author of my book was so off. Uh

thank you all for helping me Received on Thu Oct 23 2008 - 20:20:20 CEST

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