The Difference Between Primary Key and Unique Key in DB2

When it comes to database management systems like DB2, understanding the distinction between a primary key and a unique key is crucial.

Primary Key:

A primary key is a column or set of columns that uniquely identifies each record in a table. It ensures that each row in a table is distinct and serves as the main identifier for that table. Additionally, a primary key column cannot contain NULL values and there can be only one primary key per table.

Unique Key:

On the other hand, a unique key constraint in DB2 ensures that all values in a column or a set of columns are unique and not repeated within a table. Unlike a primary key, a unique key can allow NULL values, and there can be multiple unique keys defined in a table.

Therefore, the main difference between a primary key and a unique key in DB2 lies in their uniqueness constraints and the handling of NULL values.