An Introduction to Database Normalization

Short Description
When users ask for advice about their database applications, one of the first things I try to help them with is the normalization of their table structure. Normalization is the process of removing redundant data from your tables in order to improve storage efficiency, data integrity and scalability. This improvement is balanced against an increase in complexity and potential performance losses from the joining of the normalized tables at query-time.

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Content
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Let’s take a look at some issues involved in this table design:
First, this table is not very efficient with storage. Lets imagine for a second that Luke and Laura were extremely busy writers and managed to produce 500 books for our database. The combination of their two names is 25 characters long, and since we will repeat their two names in 500 rows we are wasting 25 × 500 = 12,500 bytes of storage space unnecessarily.
Second, this design does not protect data integrity. Lets once again imagine that Luke and Laura have written 500 books. Someone has had to type their names into the database 500 times, and it is very likely that one of their names will be misspelled at least once (i.e.. Thompson instead of Thomson). Our data is now corrupt, and anyone searching for book by author name will find some of the results missing. The same thing could happen with publisher name. Sams publishes hundreds of titles and if the publisher’s name were misspelled even once the list of books by publisher would be missing titles.
Third, this table does not scale well. First of all, we have limited ourselves to only two authors, yet some books are written by over a dozen people. This kind of limitation is often exhibited in personal info tables where the typical design includes Phone1, Phone2, and Phone3 columns. In both cases we are limiting future growth of our data. Another limitation to scalability is that fact that with all our data in one table our one table file will grow faster and we will have more trouble with file size limitations of our underlying operating system.
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