例如,
我有这个触发器
CREATE OR REPLACE TRIGGER SAL_REDUCE
BEFORE UPDATE ON DRIVER --or insert--
FOR EACH ROW
BEGIN
IF(NEW.SAL < 1000) THEN
RAISE_APPLICATION_ERROR(-20001,'SALARY CANNOT BE REDUCED!!! PAY THEM MORE');
END IF;
END;
/
和这个触发器
CREATE OR REPLACE TRIGGER Salary_check
BEFORE INSERT OR UPDATE OF Sal, Job ON Emp99
FOR EACH ROW
DECLARE
Minsal NUMBER;
Maxsal NUMBER;
Salary_out_of_range EXCEPTION;
BEGIN
/* Retrieve the minimum and maximum salary for the
employee's new job classification from the SALGRADE
table into MINSAL and MAXSAL: */
SELECT Minsal, Maxsal INTO Minsal, Maxsal FROM Salgrade
WHERE Job_classification = :new.Job;
IF (:new.Sal < Minsal OR :new.Sal > Maxsal) THEN
RAISE Salary_out_of_range;
END IF;
EXCEPTION
WHEN Salary_out_of_range THEN
Raise_application_error (-20300,
'Salary '||TO_CHAR(:new.Sal)||' out of range for '
||'job classification '||:new.Job
||' for employee '||:new.Ename);
WHEN NO_DATA_FOUND THEN
Raise_application_error(-20322,
'Invalid Job Classification '
||:new.Job_classification);
END;
/
因此,在第二个示例中,您注意到我在标题上描述的 :new 的用法,在第一个示例中,不带冒号的 new 用法。 这两者有什么区别?
谢谢!
第一个触发器在语法上不正确。正如尼古拉斯已经评论的那样,触发器体内需要:new
。
唯一需要new.
的地方是在触发器定义的WHEN
子句中。例如:
CREATE OR REPLACE TRIGGER SAL_REDUCE
BEFORE UPDATE ON DRIVER --or insert--
FOR EACH ROW
WHEN (NEW.SAL > 100)
BEGIN
IF(:NEW.SAL < 1000) THEN
RAISE_APPLICATION_ERROR(-20001,'SALARY CANNOT BE REDUCED!!! PAY THEM MORE');
END IF;
END;
/
在这个愚蠢的人为示例中,触发器仅在SAL
超过 100 时触发。