Java Glossary : normal form

Last updated 2004-06-28 by Roedy Green ©1996-2004 Canadian Mind Products

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normal form

In SQL, there are five rules of sensible database design called the five normal forms. Briefly they are:

1. No repeating groups of data within a row. Instead of having an Author1, Author2 and Author3 field, you should put the Author information in a separate table.
2. Every non-key item must depend on the entire primary key. Don't replicate data that depends only on part of the key.
3. Each non-key item must be a fact about the primary key item, not some other non-key item.
4. Don't mix two different one to many relationships in the same table.
5. Break tables up as small as possible so that each fact is recorded in only one place in the database. In practice, you have to balance this general rule against the extra overhead of many small tables.

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