Microsoft® SQL Server 2012 Unleashed

Referential Integrity

Referential integrity preserves the defined relationships between tables. You can define such a relationship in SQL Server by relating foreign key columns on one table to the primary key or unique key of another table. When it is defined, referential integrity ensures that values inserted in the foreign key columns have corresponding values in the primary table. It also controls changes to the primary key table and ensures that related foreign key rows are not left orphaned.