Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!pt.cs.cmu.edu!andrew.cmu.edu!rz02+
From: rz02+@andrew.cmu.edu (Rudolph R. Zung)
Newsgroups: comp.databases
Subject: Re: Do you normalize?
Message-ID: <0YlX5uy00WB5E4QsNl@andrew.cmu.edu>
Date: 20 Jul 89 20:09:30 GMT
Organization: Mathematics, Carnegie Mellon, Pittsburgh, PA
Lines: 33


Normalization is a process of specifying the structure of the database
to excise any anomalies in it. The anomalies in this case would be
instances where certain operations on the database might render it to
be inconsistent (eg if a piece of information is stored in more than
one location, a change in that number in one location would render
the other instances of that number to be inconsistent.)
eg
 Customer:("Adams, James", "1 Elm Street", "555-1212")
 Order:("Adams, James", "555-1212", "3 pounds suger")

Now if James Adams changes his address (and hence phone) before the
order is processed, then the order table would have a wrong phone number
listed, unless someone went in to changed every instance of "555-1212"
in the order table.

Any good IS/DBMS book should be able to tell you the various normal forms.
Each normal form (1NF, 2NF, 3NF...) prevents a specific anomaly. It's a
little hard to fully explain in a bb post.


...Rudy

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