A data manipulation trigger (DML trigger), is a trigger that fires in response to a DML statement (such as INSERT, UPDATE, DELETE, or TRUNCATE) that is executed against a particular table. DML triggers are defined by means of the following:
- A name
- A timing for when the trigger should react
- An event that fires the trigger
- The table over which the trigger is fired
- The level, which is the set of data handled by the trigger
The event is any of the supported DML statements: INSERT, UPDATE, DELETE, or TRUNCATE.
The timing indicates whether the trigger should react before or after the event (the DML statement) completes. It can therefore be one of the following choices:
- BEFORE: This means that the trigger is executed before the event consolidates the data
- AFTER: This means that the trigger executes after the event has consolidated data
- INSTEAD OF: This is...