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Re: 3vl 2vl and NULL

From: dawn <dawnwolthuis_at_gmail.com>
Date: 17 Feb 2006 15:00:39 -0800
Message-ID: <1140217239.824457.201590@g44g2000cwa.googlegroups.com>

Gene Wirchenko wrote:
> On 17 Feb 2006 14:21:47 -0800, "dawn" <dawnwolthuis_at_gmail.com> wrote:
>
> [snip]
>
> >Although Date now defines 1NF differently, I think he has been
> >consistent in defining "normalization" to be equivalent to 1NF. p149
>
> Reading for comprehension would help!

What did I not understand?

>
> For example, there is this
> (<http://www.dbdebunk.com/page/page/622124.htm>):
> Chris Date Responds: Normal forms--Classical normalization theory
> admits of no level of normalization higher than fifth. Fifth is
> final, for reasons explained in AN INTRODUCTION TO DATABASE SYSTEMS."

p. 149
"every tuple contains exactly one value for each of its attributes; thus, it certainly follows that every tuple in every relation contains exactly one value for each of its attributes. A relation that satisfies this property is said to be <strong>normalized</strong>, or equivalently to be in <strong>first normal form</strong>, 1NF."

p. 351
"we can say that relvars (and relations) are always in <strong>first normal form</strong> (abbreviated 1NF). In other words, "normalized" and "1NF" mean <em>exactly the same thing</em>--though you should be aware that the term <em>normalized</em> is often used to mean one of the higher levels of normalization (typically <em>third</em> normal form, 3NF); this latter usage is sloppy but very common."

I have chosen not to be sloppy in this regard even if it is common. --dawn Received on Fri Feb 17 2006 - 17:00:39 CST

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