oracle觸發器學習筆記

 引用http://www.cnblogs.com/huyong/archive/2011/04/27/2030466.html很強大

觸發器是指特定事件發生後，觸發執行用戶定義好的事件。

 

例1: 建立一個觸發器, 當職工表 emp 表被刪除一條記錄時，把被刪除記錄寫到職工表刪除日誌表中去。

 

CREATE TABLE emp_his AS SELECT * FROM EMP WHERE 1=2; 
CREATE OR REPLACE TRIGGER tr_del_emp 
   BEFORE DELETE --指定觸發時機爲刪除操作前觸發
   ON scott.emp 
   FOR EACH ROW   --說明創建的是行級觸發器 
BEGIN
   --將修改前數據插入到日誌記錄表 del_emp ,以供監督使用。
   INSERT INTO emp_his(deptno , empno, ename , job ,mgr , sal , comm , hiredate )
       VALUES( :old.deptno, :old.empno, :old.ename , :old.job,:old.mgr, :old.sal, :old.comm, :old.hiredate );
END;
DELETE emp WHERE empno=7788;
DROP TABLE emp_his;
DROP TRIGGER del_emp;

 

例2：限制對Departments表修改（包括INSERT,DELETE,UPDATE）的時間範圍，即不允許在非工作時間修改departments表。

CREATE OR REPLACE TRIGGER tr_dept_time
BEFORE INSERT OR DELETE OR UPDATE 
ON departments
BEGIN
 IF (TO_CHAR(sysdate,'DAY') IN ('星期六', '星期日')) OR (TO_CHAR(sysdate, 'HH24:MI') NOT BETWEEN '08:30' AND '18:00') THEN
     RAISE_APPLICATION_ERROR(-20001, '不是上班時間，不能修改departments表');
 END IF;
END;

 

 例3：限定只對部門號爲80的記錄進行行觸發器操作

CREATE OR REPLACE TRIGGER tr_emp_sal_comm
BEFORE UPDATE OF salary, commission_pct
       OR DELETE
ON HR.employees
FOR EACH ROW
WHEN (old.department_id = 80)
BEGIN
 CASE
     WHEN UPDATING ('salary') THEN
        IF :NEW.salary < :old.salary THEN

           RAISE_APPLICATION_ERROR(-20001, '部門80的人員的工資不能降');
        END IF;
     WHEN UPDATING ('commission_pct') THEN

        IF :NEW.commission_pct < :old.commission_pct THEN
           RAISE_APPLICATION_ERROR(-20002, '部門80的人員的獎金不能降');
        END IF;
     WHEN DELETING THEN
          RAISE_APPLICATION_ERROR(-20003, '不能刪除部門80的人員記錄');
     END CASE;
END; 

/*
實例：
UPDATE employees SET salary = 8000 WHERE employee_id = 177;
DELETE FROM employees WHERE employee_id in (177,170);
*/

 

例4：利用行觸發器實現級聯更新。在修改了主表regions中的region_id之後（AFTER），級聯的、自動的更新子表countries表中原來在該地區的國家的region_id。

 

CREATE OR REPLACE TRIGGER tr_reg_cou
AFTER update OF region_id
ON regions
FOR EACH ROW
BEGIN
 DBMS_OUTPUT.PUT_LINE('舊的region_id值是'||:old.region_id
                  ||'、新的region_id值是'||:new.region_id);
 UPDATE countries SET region_id = :new.region_id
 WHERE region_id = :old.region_id;
END;

 

 例5：在觸發器中調用過程。

CREATE OR REPLACE PROCEDURE add_job_history
 ( p_emp_id          job_history.employee_id%type
   , p_start_date      job_history.start_date%type
  , p_end_date        job_history.end_date%type
   , p_job_id          job_history.job_id%type
   , p_department_id   job_history.department_id%type
   )
IS
BEGIN
 INSERT INTO job_history (employee_id, start_date, end_date,
                           job_id, department_id)
  VALUES(p_emp_id, p_start_date, p_end_date, p_job_id, p_department_id);
END add_job_history;

--創建觸發器調用存儲過程...
CREATE OR REPLACE TRIGGER update_job_history
 AFTER UPDATE OF job_id, department_id ON employees
 FOR EACH ROW
BEGIN
 add_job_history(:old.employee_id, :old.hire_date, sysdate,
                  :old.job_id, :old.department_id);
END;