Re: Why spurious tuples with fifth normal form?

From: Jan Hidders <jan.hidders_at_REMOVETHIS.pandora.be>
Date: Fri, 17 Jun 2005 19:22:58 GMT
Message-ID: <mqFse.123639$uh6.6996063@phobos.telenet-ops.be>

Ahem. *cough* Just checking if you guys were paying attention. :-)

Jan Hidders wrote:
>
> step 1. H = { ABC, ABD, CE }
> step 2. (#1) H = { ABCD, CE } (because ABC and ABC share the c.k. AB)

                                                  ^^^

Should be "ABD"

> step 2. (#2) H = { ABCDE } (because ABCDE and CE share the c.k. C)

                                       ^^^^^ 

Should be "ABCD"

> step 3. no more two distinct components with common cand. key
> step 4. The JD is implied by the cand. keys because ABCDE is in H
>
> So even though this join dependency holds, you do not have to split.

That's still correct. :-)

• Jan Hidders

Received on Fri Jun 17 2005 - 14:22:58 CDT