Re: Normalization and Derived Information
Date: Thu, 23 Sep 2004 08:48:10 -0400
Message-ID: <YYedna1KtIy4W8_cRVn-iQ_at_comcast.com>
"--CELKO--" <jcelko212_at_earthlink.net> wrote in message news:18c7b3c2.0409221847.2c7cc2c6_at_posting.google.com...
> It is bad if you materialize the computed column because it can get
> out of synch with the columns used to compute it. We used to have
> that problem all the time in punch card systems.
This issue arises whenever you materialize computable data. You have to recognize that, if you do this (materializing price*quantity) you take on the responsibility for maintaining consistency in the database.
The reason I use extended price in a star schema has nothing to do with the legacy of punched cards. It has to do with the way Kimball recommends building the data warehouse, or the data mart. Received on Thu Sep 23 2004 - 14:48:10 CEST