Cascading referential integrity constraints are automatic updates and deletes on dependant objects. They define a set of actions that SQL server may need to take. The References clause of the CREATE TABLE and ALTER TABLE statements support ON DELETE and ON UPDATE clauses:

[ON DELETE {NO ACTION} ]: If an attempt to delete a row is made, with a key referenced by foreign keys in existing rows in other tables, an error is raised and DELETE is rolled back.

[ON UPDATE {NO ACTION } ]: If an attempt to update a row is made, with a key referenced by foreign keys in existing rows in other tables, an error is raised and UPDATE is rolled back.

[ ON DELETE { CASCADE } ]: If an attempt to delete a row is made, with a key referenced by foreign keys in existing rows in other tables, all rows containing those foreign keys are also deleted

[ ON UPDATE { CASCADE } ]: If an attempt to update a row is made, with a key referenced by foreign keys in existing rows in other tables, all rows containing those foreign keys are also Updated.

NO ACTION is default.