Types of triggers v16

EDB Postgres Advanced Server supports row-level and statement-level triggers.

• A row-level trigger fires once for each row that's affected by a triggering event. For example, suppose deletion is defined as a triggering event on a table, and a single DELETE command is issued that deletes five rows from the table. In this case, the trigger fires five times, once for each row.

• A statement-level trigger fires once per triggering statement, regardless of the number of rows affected by the triggering event. In the previous example of a single DELETE command deleting five rows, a statement-level trigger fires only once.

You can define the sequence of actions regarding whether the trigger code block executes before or after the triggering statement for statement-level triggers. For row-level triggers, you can define whether the trigger code block executes before or after each row is affected by the triggering statement.

• In a before row-level trigger, the trigger code block executes before the triggering action is carried out on each affected row. In a before statement-level trigger, the trigger code block executes before the action of the triggering statement is carried out.

• In an after row-level trigger, the trigger code block executes after the triggering action is carried out on each affected row. In an after statement-level trigger, the trigger code block executes after the action of the triggering statement is carried out.

In a compound trigger, you can define a statement-level and a row-level trigger in a single trigger and fire it at more than one timing point. For details, see Compound triggers.