Third normal form (3NF) is a database principle that supports data integrity by building on the database normalization principles provided by first normal form (1NF) and second normal form (2NF). The goal of 3NF is to improve database processing while minimizing storage costs.

There are two basic requirements for a database in 3NF:

Let’s further explore what we mean by all columns being dependent on the primary key. If the value of a column can be derived from both the primary key and another column in the table, this violates 3NF. Consider a table of employees with these columns:

Are both LastName and FirstName dependent only on the value of EmployeeID? Well, could LastName be dependent on FirstName? No, because there is nothing inherent in LastName that suggests the value of FirstName.