What is the purpose of a foreign key in a database?

The purpose of a foreign key in a database is to link data between two different tables. A foreign key is a column or a set of columns in one table that refers to the primary key in another table. This relationship establishes a connection between the two tables, allowing for the enforcement of referential integrity and enabling complex queries that combine data from multiple sources.

For instance, in a database with two tables, such as "Customers" and "Orders," the "Orders" table may include a foreign key that references the primary key in the "Customers" table. This ensures that each order is associated with a valid customer, thus forming a meaningful relationship. By utilizing foreign keys, databases can efficiently manage data relationships and maintain data integrity across multiple tables.