Normalizing the Data › Normal Forms of Data

Normal Forms of Data

All normalized data tables exist in one of the following normal forms:

• First normal form
• Second normal form
• Third normal form

A data table that exists in a particular normal form complies with the rules that define that form. A table that exists in second normal form satisfies the criteria for first normal form; in addition, a table in third normal form satisfies the criteria for both first and second normal forms.

Goal of normalization

Since the rules of third normal form are the most rigorous, they are also the most desirable. The goal of the normalization process is to create data tables that are organized in third normal form.

Note: Several database theorists have suggested that tables in third normal form can be broken down into even simpler structures. For example, some theorists recommend that tables be organized in fourth or fifth normal form. However, at the present time, it seems most practical to organize data tables in third normal form.

The first, second, and third normal forms of data organization are discussed in the following sections.