Re: To Denormalise or not to Denormalise

Your friend, the theorist, wouldn't get very far in the day-to-day usage of his database. In fact it would be interesting to see if anyone here is working with, or has ever worked with, a moderate-sized database (say 20G or more) that is completely normalized. I've never seen one.

Van

Brian Peasland <peasland_at_edcmail.cr.usgs.gov> wrote in message news:3906E5CB.874B3579_at_edcmail.cr.usgs.gov...
> I don't want to repeat any of the previous replies. They all have good
> points. I do want to add that one can think of clustered tables as sort
> of denormalizing two tables. Oracle added this feature to help improve
> performance under certain conditions. Although in my opinion, you could
> just denormalize two table and do away with the cluster structure.
>
> HTH,
> Brian
>
> Billy Verreynne wrote:
> >
> > "Lawrence" <lsimela_at_mahalini.prestel.co.uk> wrote:
> >
> > >I wonder if any of you folk out there can help settle an argument with
 a
> > >colleague who passionately believes that one should never have to
> > >denormalise any part of a well designed database. He believes that a
 'well
> > >designed' database should be in 3NF or higher and can be efficiently
> > >implemented without denormalising any part of it.
> >
> > That entirely depends on the nature of the database. Implementing 3NF
> > for a datamart or data warehouse is commiting performance suicide.
> >
> > Back in the 80's design methodologies were quite the topic. One of
> > these were called Tetrach. The primary purpose was to gather enough
> > data during the analysis and design phases, in order to simulate
> > performance loads using a maths model. Was interesting back then, as
> > in once case study (part of the advance course in Tetrach A&D) showed
> > that how implementing an invoice in 3NF could cause a business to fail
> > to process a single day's average load of orders (given the existing
> > hardware platform used by the business). Denormalising the invoice
> > solved this performance problem and potentially saved the company from
> > not being able to fill the orders, or spend a lot of money of a very
> > expensive hardware upgrade. Of course, back then we measured memory in
> > KB and not MB or even GB.. :-)
> >
> > I am not sure what the argument is with your friend though. A well
> > designed database in 3NF is a well designed database if the aim is to
> > create a relational database. No question about that. However, that is
> > only one slice of the pie that makes up a corporate system. From a
> > theoretical point of view, you can view that slice in isoltaion. From
> > a real word business view, you simply can not. A well designed
> > database means nothing the business if it can not deliver - no matter
> > how good or tasty that single slice is, it is the whole pie that is
> > consumed by the business.
> >
> > regards,
> > Billy
>
> --
> ========================================
> Brian Peasland
> Raytheons Systems at
> USGS EROS Data Center
> These opinions are my own and do not
> necessarily reflect the opinions of my
> company!
> ========================================
Received on Wed Apr 26 2000 - 00:00:00 CDT