DML Triggers
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CREATE
[OR REPLACE] TRIGGER trigger_name
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The components of the syntax are:
- trigger_name
trigger_name uniquely identifies the trigger.
- timing
Timing indicates when the trigger fires in relation to the triggering event. Values are BEFORE, AFTER or INSTEAD OF.
- event
Event identifies the DML operation causing the trigger to fire. Values are INSERT, UPDATE and DELETE.
- object_name
object_name indicates the table or view associated with the trigger.
- REFERENCING
REFERENCING clause is used to choose a correlation name for referencing the old and new values of the current row.
- WHEN
WHEN clause is used to apply a conditional predicate, in parentheses, which is evaluated for each row to determine whether or not to execute the trigger body.
- trigger_body
The trigger_body is the action performed by the trigger.
- Statement
trigger
A statement trigger is the default type of trigger and executes once for the triggering event. A statement trigger fires even if now rows are affected at all.
- Row
trigger.
A row trigger executes once for each row affected by the triggering event. A row trigger is not executed if the triggering event does not affect any rows. To indicate a row trigger, the FOR EACH ROW clause is specified.