Normalizing the Database (Part 3 of 5), Second Normal Form
Before we get into second normal form (2NF), note that if the primary key is a single column, or all the columns in the table are part of the primary key, then the table is already in second normal form.
A table in second normal form must be in first normal form and have no partial functional dependencies.
A partial functional dependency is when some, but not all of a composite key’s values determine a non-key column’s value.
To avoid this, a second normal form table is fully functionally dependent. That means that all non-key attributes (or columns) must depend on all components of the key. If the table has some non-key attributes that do not depend on all components of the key, break the table up into two or more tables so that, in each table, all non-key attributes depend on all components of the primary key.

