1. Database PL/SQL Language Reference
  2. PL/SQL Triggers
  3. Order in Which Triggers Fire

Order in Which Triggers Fire

If two or more triggers with different timing points are defined for the same statement on the same table, then they fire in this order:

  1. All BEFORE STATEMENT triggers

  2. All BEFORE EACH ROW triggers

  3. All AFTER EACH ROW triggers

  4. All AFTER STATEMENT triggers

If it is practical, replace the set of individual triggers with different timing points with a single compound trigger that explicitly codes the actions in the order you intend. For information about compound triggers, see "Compound DML Triggers".

If you are creating two or more triggers with the same timing point, and the order in which they fire is important, then you can control their firing order using the FOLLOWS and PRECEDES clauses (see "FOLLOWS | PRECEDES").

If multiple compound triggers are created on a table, then:

  • All BEFORE STATEMENT sections run at the BEFORE STATEMENT timing point, BEFORE EACH ROW sections run at the BEFORE EACH ROW timing point, and so forth.

    If trigger execution order was specified using the FOLLOWS clause, then the FOLLOWS clause determines the order of execution of compound trigger sections. If FOLLOWS is specified for some but not all triggers, then the order of execution of triggers is guaranteed only for those that are related using the FOLLOWS clause.

  • All AFTER STATEMENT sections run at the AFTER STATEMENT timing point, AFTER EACH ROW sections run at the AFTER EACH ROW timing point, and so forth.

    If trigger execution order was specified using the PRECEDES clause, then the PRECEDES clause determines the order of execution of compound trigger sections. If PRECEDES is specified for some but not all triggers, then the order of execution of triggers is guaranteed only for those that are related using the PRECEDES clause.

    Note:

    PRECEDES applies only to reverse crossedition triggers, which are described in Oracle Database Development Guide.

The firing of compound triggers can be interleaved with the firing of simple triggers.

When one trigger causes another trigger to fire, the triggers are said to be cascading. The database allows up to 32 triggers to cascade simultaneously. To limit the number of trigger cascades, use the initialization parameter OPEN_CURSORS (described in Oracle Database Reference), because a cursor opens every time a trigger fires.