Re: DB Design Principles for RDBMS
Date: 7 Mar 2003 11:16:31 +0100
>"Tony" <andrewst_at_onetel.net.uk> wrote in message
>> Anton Versteeg <anton_versteeg_at_nnll.iibbmm.com> wrote in message
>> > 4. Do not over-normalize your database design
>> I'm not sure how useful that advice is to someone new to database
>> design. They may think: "Hmmm... having to join from order_line to
>> order to get the customer name is a bit much - let's not take
>> normalisation THAT far!"
>I read somewhere that it is a good idea to start with a fully normalised db
>then selectively denormalise only when you have a good reason to do so.
While in itself not a bad rule of thumb it is of course no alternative for actually weighing the costs an benifits of every denormalization step that you take. Many people forget that denormalizing means that you have to introduce extra database constraints or run the risc of inconsistent data, and these extra constraints may actually hurt your performance.
- Jan Hidders