Re: Advanced SQL

From: Jan Hidders <>
Date: Fri, 07 Sep 2007 13:59:45 -0000
Message-ID: <>

On 7 sep, 15:43, Jon Heggland <> wrote:
> Quoth Evan Keel:

> > "David Portas" <> wrote in message
> >
> >> Call me picky but I am not entirely comfortable with that U.Texas site,
> >> even though it's a commendable effort overall.
> >> "The definition of second normal form states that only tables with
> >> composite primary keys can be in 1NF but not in 2NF"
> > They have it right here. All non-key attributes must be dependent on the
> > full key. Only applies to tables with keys composed of multiple columns>
> No. There may be dependencies where the left side is empty.

In that case the declared candidate key is not really a candidate key. Under the assumption that the declared candidate keys are indeed candidate keys, the claim is correct.

> But it's a
> common mistake. If I remember correctly, one of my database textbooks
> "proves" that any relvar with just two attributes is automatically in BCNF.

Under the assumption that I just mentioned, that claim is actually also correct.

  • Jan Hidders
Received on Fri Sep 07 2007 - 15:59:45 CEST

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