Triggers

Do one action in the trigger

CREATE TRIGGER testref BEFORE INSERT ON test1
  FOR EACH ROW
    INSERT INTO test2 SET a2 = NEW.a1;

Do more actions in one trigger

delimiter |
 
CREATE TRIGGER testref BEFORE INSERT ON test1
  FOR EACH ROW BEGIN
    INSERT INTO test2 SET a2 = NEW.a1;
    DELETE FROM test3 WHERE a3 = NEW.a1;
    UPDATE test4 SET b4 = b4 + 1 WHERE a4 = NEW.a1;
  END;
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