What feature does the foreign key constraint provide?

The foreign key constraint primarily serves the purpose of linking data between tables in a relational database. By establishing a foreign key relationship, a table can reference a primary key from another table, thus creating a defined connection between the two sets of data. This relationship ensures data integrity and enables complex queries that leverage the relationships among different tables.

For instance, if you have a 'Customers' table and an 'Orders' table, the orders can reference customer IDs through a foreign key. This ensures that every order is associated with a valid customer, maintaining the relational nature of the data and enabling meaningful connections and data retrieval across the tables.

Understanding this concept is crucial because foreign key constraints help maintain referential integrity by preventing orphaned records, which occur when a reference points to a non-existent record in another table. This means that as long as the foreign key relationships are valid, any operations that involve adding, modifying, or deleting records will be better managed, reinforcing the accuracy and coherence of your database.