Primary Key

In relational database design, a primary key is a key used to uniquely identify each row in a table. A primary key comprises a single column or a set of columns. No two distinct rows in a table can have the same value (or combination of values) in those columns. Only one primary key can be in a table.

The values in a primary key are not allowed to be NULL.

Primary keys can be referenced by foreign keys.

See Also

• Foreign Key