Developing a Conceptual Model › Normalizing Your Data Model › Step 3: Creating Third Normal Form (3NF)

Step 3: Creating Third Normal Form (3NF)

An entity is in third normal form (3NF) if it is in second normal form (2NF) and each of its non-key attributes is not dependent on another non-key attribute.

The Supplier entity is in 2NF and must be put into 3NF:

Supplier

K     Supplier number

 Supplier name

   Supplier status

 Supplier status description

Supplier Status Description is functionally dependent on Supplier Status. Third normal form requires that the entity Supplier be split into two entities: Supplier and Supplier Status. You define the entity Supplier as follows:

You then define Supplier Status, as follows:

Supplier Status

K    Supplier status

 Supplier status description

You can now maintain Supplier Status information separately. A change to a Supplier Status Description does not require an update to the Supplier instance.

With third normal form, all attributes in an entity are fully functionally dependent on only the entire key of the entity.