Triggers are stored programs, which are automatically executed or fired when some events occur. Triggers are, in fact, written to be executed in response to any of the following events −
- A database manipulation (DML) statement (DELETE, INSERT, or UPDATE).
- A database definition (DDL) statement (CREATE, ALTER, or DROP).
- A database operation (SERVERERROR, LOGON, LOGOFF, STARTUP, or SHUTDOWN).
Triggers could be defined on the table, view, schema, or database with which the event is associated.
Benefits of Triggers
Triggers can be written for the following purposes −
- Generating some derived column values automatically
- Enforcing referential integrity
- Event logging and storing information on table access
- Synchronous replication of tables
- Imposing security authorizations
- Preventing invalid transactions