Re: Getting Normal Forms *wrong*. Is there actual disagreement on what 1NF > 3NF means or is this sloppiness or ignorance on authors' parts?

From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Fri, 07 Aug 2009 20:00:28 -0300
Message-ID: <4a7cb20d$0$23773$9a566e8b_at_news.aliant.net>


David Portas wrote:

> "Bob Badour" <bbadour_at_pei.sympatico.ca> wrote in message
> news:4a7c6737$0$23786$9a566e8b_at_news.aliant.net...
>

>>>Here's something I really need clarification on. Is it the case, or is
>>>it *not* the case, that 2NF "only applies" in cases where there is a
>>>composite key?
>>
>>It is the case.

>
> Here's a relation:
>
> Triangles {Id*, Area, SumOfAngles}
>
> * = key. The following dependency holds because the sum of the angles of any
> triangle is a constant:
>
> {}->{SumOfAngles}
>
> {} (the empty set) is a proper subset of the key {Id} and {}->{SumOfAngles}
> is a dependency on only part of the key. Triangles is a relation without a
> composite key and it violates 2NF. I don't see why 2NF shouldn't apply to
> this case, even though it's unusual and not especially interesting.

I sit corrected. Thank you! Received on Sat Aug 08 2009 - 01:00:28 CEST

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