Typical uses for triggers include combinations of the following:
Cascading deletes —A delete operation on one table causes additional rows to be deleted from other tables that are related to the first table by key values. This is an active way of enforcing referential integrity that a table constraint enforces passively.
Cascading updates — An update operation on one table causes additional rows to be updated in other tables that are related to the first table by key values. These updates are commonly limited to the key fields themselves. This is an active way of enforcing referential integrity that a table constraint enforces passively.
Summation updates — An update operation in one table causes an update operation in a row of another table. The second value is increased or decreased.
Automatic archiving — A delete operation on one table creates an identical row in an archive table that is not otherwise used by the database.
Cascading deletes —A delete operation on one table causes additional rows to be deleted from other tables that are related to the first table by key values. This is an active way of enforcing referential integrity that a table constraint enforces passively.