Foreign Key

Foreign keys are used to identify records stored in other database tables that are related to the records in the current table. The following table contains a list of departments.

Primary Key	Department
1	Sales
2	Marketing
3	Support

The following table contains employee data.

Primary Key	Department	First Name	Last Name
1	3	Betty	Miller
2	2	Sam	Cook
3	2	Ralf	Miller
4	1	Sam	Hampton

The department's primary key is stored here as a foreign key in the "Department" column. This makes it very easy to determine, for example, that Betty Miller works in the Support department.