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Normal Form

You won’t get too far into most database design books without reading a discussion on normalization and the Normal Forms. The Normal Forms are a series of forms, or table design specifications, that describe the best way to lay out data in a database. The higher the normal form, the more normalized the database is. Each form builds on the previous one, adding additional rules or conditions that must be met. Normalization is the process of removing data duplication, more clearly defining key relationships, and generally moving towards a more idealized database form. It is possible for different tables in the same database to be at different levels.

Most people recognize five normal forms simply referred to as the First Normal Form through the Fifth Normal Form. These are often abbreviated 1NF through 5NF. There are also a few named forms, such as the Boyce-Codd Normal Form (BCNF). Most of these other forms are roughly equivalent to one of the numbered forms. For example, BCNF is a slight extension to the Third Normal Form. Some folks also recognize higher levels of normalization, such as a Sixth Normal Form and beyond, but these extreme levels of normalization are well beyond the practical concerns of most database designers.

Normalization

The normalization process is useful for two reasons. First, normalization specifies design criteria that can act as a guide in the design process. If you have a set of tables that are proving to be difficult to work with, that often points ...