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

A foreign key serves as a crucial component in relational database design by creating a direct link between two tables. This link references the primary key of another table, thereby establishing a relationship that helps maintain the logical connections between different sets of data. For instance, if one table contains customer information, and another table contains order details, the foreign key in the order table will point to the primary key in the customer table. This relationship allows for queries that can seamlessly join data from both tables based on the common link established by the foreign key. Such connections not only enhance data organization but also enable powerful data retrieval operations that reflect real-world relationships.

In addition to forming these relationships, foreign keys play an essential role in ensuring data integrity across tables. They enforce referential integrity by preventing actions that would lead to orphan records—entries in the referencing table that do not have a corresponding entry in the referenced table. The other options, while related to database operations, do not encapsulate the primary function of a foreign key as effectively as the linking of tables that is highlighted in the correct option.