Procedural code automatically executed in response to a database event.
A database trigger is procedural code that runs automatically in response to an event on occurring on the database. Triggers are commonly used for events on tables and views where they typically help maintain data integrity.
Table events that can fire triggers include:
- Insert (Before, After) (Statement, Row)
- Update (Before, After) (Statement, Row)
- Delete (Before, After) (Statement, Row)
Some platforms include other events such as:
- DDL Triggers (SQL Server, Oracle - Can be schema specific)
- DB Level Triggers (Firebird, Oracle)
- Compound Triggers (Oracle)
- Instead Of Triggers (Oracle)
- System Triggers such as Startup, Shutdown, and Server Error (Oracle)
- Allowances for CREATE TABLE within Standard Events (PostgreSQL)