Introduction « Trigger « Oracle PL/SQL Tutorial

28.1.1.A trigger is an event within the DBMS that can cause some code to execute automatically.
28.1.2.Placing triggers on tables
28.1.3.Trigger Which Modifies a Mutating Table
28.1.4.Solution for the Mutating Tables Problem
28.1.5.Raise Exception from trigger
28.1.6.Trigger for auditing
28.1.7.Trigger with a REFERENCING clause
28.1.8.Trigger with REFERENCING and WHEN clauses
28.1.9.Trigger with multiple triggering events