Re: On Normalisation & the State of Normalisation

Op donderdag 5 februari 2015 17:44:06 UTC+1 schreef Nicola:
> In article <a24a286a-4212-40b3-bcee-782ca8bd2d0b_at_googlegroups.com>,
> Erwin wrote:
>
> > Op donderdag 5 februari 2015 15:05:08 UTC+1 schreef Nicola:
> > > In article <>,
> > > Jan Hidders wrote:
> > >
> > > > > 1. The developer declares that the proposed extension satisfies 5NF.
> > > > > Is
> > > > > that correct ? If not, please state why, which NF is breaks, any
> > > > > errors
> > > > > that it may have, etc. A few words will suffice. I expect minimal
> > > > > discussion, but don't let me stop you.
> > > >
> > > > Yes, it is in 5NF. But it is not dependency preserving.
> > >
> > > Which dependencies are not preserved? With respect to what schema?
> > >
> > > Nicola
> > >
> >
> > If I tell him that, he tells me to learn to read.
>
> Jan?

I'm afraid I have to back-pedal here. The dependency I had in mind is actually preserved after all.

What I was thinking of is the following. We were told that the CountryCode and StateCode are ISO 3166-1 and 3166-2. Now, ISO 3166-2 actually contains the country code from ISO 3166-1. So if you would join everything into a single table (Universal Relation, and all that) there would be an FD StateCode -> CountryCode. In the current schema that FD no longer lives in one of the relations, but I had missed that it actually follows from the local FDs / CKs.

Showing this is left to the reader as an exercise. :-)

• Jan Hidders