Database Normalization Overview

Database Normalization Overview

Use Normalization to reduce redundancy in your logical data model.

Method

Apply the rules of Normalization while conducting Entity-Relationship Modelling. The basic steps in the normalization process result in data structures which are in:

1. First Normal Form,
   
2. Second Normal Form,
   
3. Third Normal Form.

These three normal forms are designed to prevent update anomalies and data inconsistencies. First normal form is concerned with the shape of the record and the preliminary identification of keys. Second normal form and third normal form are concerned with resolving problems associated with the interrelationship of keys and dependent attributes.

Other normal forms include Boyce-Codd, fourth, and fifth. Boyce-Codd normal form eliminates redundancy that can sometimes occur even in third normal form tables. Fourth normal form eliminates multi-dependence, which occurs when there are two independent many-to-many relationships. Fifth normal form eliminates cyclic dependency, which involves a three-way relationship among three attributes. In practice, fourth normal form occurs intuitively as part of the exercise to produce third normal form. Boyce-Codd normal form and fifth normal form are difficult to use and rarely needed.