Re: Normalization and Derived Information

"Kenneth Downs" <firstinit.lastname_at_lastnameplusfam.net> wrote in message news:367sic.063.ln_at_mercury.downsfam.net...
> I'm wondering about the precise status of derived columns in terms of 1nf,
> 2nf and so forth.

The first thing I want to say is that data normalization, considered rationally, is a design principle that you can use to avoid certain anomalies. However, too many people, including some of the denizens of this newsgroup, treat it as the sole inerrant sign of allegience to the One True Faith (OTF) of the Relational Data Model (RDM). Any design, like star schema, that deliberately settles for anything less than FULL NORMALIZATION (shouting implied), is excommunicate and anathema and it identifies the perpetrator as an infidel!

This is nonsense. It amounts to turning a useful concept into mumbo jumbo.

I think, but I'm not sure, that the Extended Price is redundant with the quantity and unit price in the same row. So it really is one fact in more than one place, and probably violates some normalization rule. Now ask me if I care. The extra few bytes of storage are probably worth it.

Just for grins, most of the usual star schema designs for this kind of data has ONLY the extended price in the fact table. The advantage of the extended price is that it can be summed. (other trivia about star schema design omitted). Received on Wed Sep 22 2004 - 21:22:12 CEST