sql plus触发器运行错误

Question

sql plus触发器运行错误
代码是书上的：

CREATE OR REPLACE TRIGGER t_verifysalary
   BEFORE UPDATE ON emp   
   FOR EACH ROW         
   WHEN(new.sal>old.sal)    
DECLARE
   v_sal   NUMBER;          
BEGIN
   IF UPDATING ('sal') THEN 
      v_sal := :NEW.sal - :OLD.sal;
      DELETE FROM emp_history 
            WHERE empno = :OLD.empno;    
      INSERT INTO emp_history           
           VALUES 
(:OLD.empno, :OLD.ename, :OLD.job, :OLD.mgr, :OLD.hiredate,:OLD.sal, :OLD.comm, :OLD.deptno);
      UPDATE emp_history                   
         SET sal = v_sal
       WHERE empno = :NEW.empno;
   END IF;
END;
/

放到sqlplus里面会报错：

警告: 创建的触发器带有编译错误。

SQL> show errors
TRIGGER T_VERIFYSALARY 出现错误:

LINE/COL ERROR

---

8/7 PL/SQL: SQL Statement ignored
8/19 PL/SQL: ORA-00947: 没有足够的值
SQL>
怎么回事呢

Answer 1