复合触发器的before语句和after语句部分的用途

在创建 compound trigger 你应该想想你想做什么。每个 复合触发器 可以拆分为多个 triggers . 如果你有多重 触发器 在一 table ,这就是要考虑的一点 复合触发器 ,将这些功能合并为一个 trigger 。

这是toad为其创建的默认模板 Compound triggers -解释得很好:

COMPOUND TRIGGER
    tmpVar NUMBER;
  BEFORE STATEMENT IS
  BEGIN
    begin
      -- we cannot reference :new or :old in the before statement section
      tmpVar := 0;
    EXCEPTION
      WHEN OTHERS THEN
       -- Consider logging the error and then re-raise
      RAISE;
    END;
  END BEFORE STATEMENT;

  BEFORE EACH ROW IS
  BEGIN
    begin
      -- we can read or write to :new or :old in the before each row section
      tmpVar := 0;
    EXCEPTION
      WHEN OTHERS THEN
       -- Consider logging the error and then re-raise
      RAISE;
    END;
  END BEFORE EACH ROW;

  AFTER EACH ROW IS
  BEGIN
    begin
      tmpVar := 0;
      -- we can read, but not write to :new or :old in the after each row section
    EXCEPTION
      WHEN OTHERS THEN
       -- Consider logging the error and then re-raise
      RAISE;
    END;
  END AFTER EACH ROW;

  AFTER STATEMENT IS
  BEGIN
    begin
      -- we cannot reference :new or :old in the after statement section
      tmpVar := 0;
    EXCEPTION
      WHEN OTHERS THEN
       -- Consider logging the error and then re-raise
      RAISE;
    END;
  END AFTER STATEMENT;
END MyTrigger;