What do foreign keys in a relational database do?

Foreign keys in a relational database serve the critical function of linking records from multiple tables. This relationship is fundamental to maintaining the integrity of the data and establishing connections between different data sets.

When a foreign key is defined in one table, it essentially creates a reference to the primary key of another table. This linkage allows for related data to be associated across tables, which is essential for performing operations such as joins. For instance, if you have a "Customers" table and an "Orders" table, a foreign key in the "Orders" table could reference the customer ID from the "Customers" table. This allows one to retrieve all orders associated with a specific customer easily.

Overall, foreign keys are vital for ensuring that data remains consistent and that relationships between different pieces of data are properly maintained in a relational database structure.