An entity is in Second Normal Form if it is in First Normal Form and each non-key attribute is fully functionally dependent on the primary key. An entity whose primary key consists of only one attribute is automatically in 2NF.
To test if the model is in 2NF, System Architect examines the primary keys associated with each non-key attribute. If it finds two entities with the same non-key attribute, it checks that the primary keys of the entities are identical.
Example
In this example, CUSTOMER ORDER is in violation of 2NF because the attributes “DATE SHIPPED”, and “FED EX NUMBER” are functionally dependent on the primary key “CUSTOMER ID”, “ORDER NUMBER” and “DATE FILLED”, whereas in CUSTOMER HISTORY they are dependent only on “CUSTOMER ID”.
