8.5 数据库触发器的应用举例
例1：创建一个DML语句级触发器，当对emp表执行INSERT, UPDATE, DELETE 操作时，它自动更新dept_summary 表中的数据。由于在PL/SQL块中不能直接调用DDL语句，所以，利用ORACLE内置包DBMS_UTILITY中的EXEC_DDL_STATEMENT过程，由它执行DDL语句创建触发器。
CREATE TABLE dept_summary(
Deptno NUMBER(2),
Sal_sum NUMBER(9, 2),
Emp_count NUMBER);
INSERT INTO dept_summary(deptno, sal_sum, emp_count)
SELECT deptno, SUM(sal), COUNT(*)
FROM emp
GROUP BY deptno;
--创建一个PL/SQL过程disp_dept_summary
--在触发器中调用该过程显示dept_summary标中的数据。
CREATE OR REPLACE PROCEDURE disp_dept_summary
IS
Rec dept_summary%ROWTYPE;
CURSOR c1 IS SELECT * FROM dept_summary;
BEGIN
OPEN c1;
FETCH c1 INTO REC;
DBMS_OUTPUT.PUT_LINE('deptno sal_sum emp_count');
DBMS_OUTPUT.PUT_LINE('-------------------------------------');
WHILE c1%FOUND LOOP
DBMS_OUTPUT.PUT_LINE(RPAD(rec.deptno, 6)||
To_char(rec.sal_sum, '$999,999.99')||
LPAD(rec.emp_count, 13));
FETCH c1 INTO rec;
END LOOP;
CLOSE c1;
END;
BEGIN
DBMS_OUTPUT.PUT_LINE('插入前');
Disp_dept_summary();
DBMS_UTILITY.EXEC_DDL_STATEMENT('
CREATE OR REPLACE TRIGGER trig1
AFTER INSERT OR DELETE OR UPDATE OF sal ON emp
BEGIN
DBMS_OUTPUT.PUT_LINE(''正在执行trig1 触发器…'');
DELETE FROM dept_summary;
INSERT INTO dept_summary(deptno, sal_sum, emp_count)
SELECT deptno, SUM(sal), COUNT(*)
FROM emp GROUP BY deptno;
END;
');
INSERT INTO dept(deptno, dname, loc)
VALUES(90, ‘demo_dept’, ‘none_loc’);
INSERT INTO emp(ename, deptno, empno, sal)
VALUES(USER, 90, 9999, 3000);
DBMS_OUTPUT.PUT_LINE('插入后');
Disp_dept_summary();
UPDATE emp SET sal=1000 WHERE empno=9999;
DBMS_OUTPUT.PUT_LINE('修改后');
Disp_dept_summary();
DELETE FROM emp WHERE empno=9999;
DELETE FROM dept WHERE deptno=90;
DBMS_OUTPUT.PUT_LINE('删除后');
Disp_dept_summary();
DBMS_UTILITY.EXEC_DDL_STATEMENT(‘DROP TRIGGER trig1’);
EXCEPTION
WHEN OTHERS THEN
DBMS_OUTPUT.PUT_LINE(SQLCODE||'---'||SQLERRM);
END;
Deptno NUMBER(2),
Sal_sum NUMBER(9, 2),
Emp_count NUMBER);
INSERT INTO dept_summary(deptno, sal_sum, emp_count)
SELECT deptno, SUM(sal), COUNT(*)
FROM emp
GROUP BY deptno;
--创建一个PL/SQL过程disp_dept_summary
--在触发器中调用该过程显示dept_summary标中的数据。
CREATE OR REPLACE PROCEDURE disp_dept_summary
IS
Rec dept_summary%ROWTYPE;
CURSOR c1 IS SELECT * FROM dept_summary;
BEGIN
OPEN c1;
FETCH c1 INTO REC;
DBMS_OUTPUT.PUT_LINE('deptno sal_sum emp_count');
DBMS_OUTPUT.PUT_LINE('-------------------------------------');
WHILE c1%FOUND LOOP
DBMS_OUTPUT.PUT_LINE(RPAD(rec.deptno, 6)||
To_char(rec.sal_sum, '$999,999.99')||
LPAD(rec.emp_count, 13));
FETCH c1 INTO rec;
END LOOP;
CLOSE c1;
END;
BEGIN
DBMS_OUTPUT.PUT_LINE('插入前');
Disp_dept_summary();
DBMS_UTILITY.EXEC_DDL_STATEMENT('
CREATE OR REPLACE TRIGGER trig1
AFTER INSERT OR DELETE OR UPDATE OF sal ON emp
BEGIN
DBMS_OUTPUT.PUT_LINE(''正在执行trig1 触发器…'');
DELETE FROM dept_summary;
INSERT INTO dept_summary(deptno, sal_sum, emp_count)
SELECT deptno, SUM(sal), COUNT(*)
FROM emp GROUP BY deptno;
END;
');
INSERT INTO dept(deptno, dname, loc)
VALUES(90, ‘demo_dept’, ‘none_loc’);
INSERT INTO emp(ename, deptno, empno, sal)
VALUES(USER, 90, 9999, 3000);
DBMS_OUTPUT.PUT_LINE('插入后');
Disp_dept_summary();
UPDATE emp SET sal=1000 WHERE empno=9999;
DBMS_OUTPUT.PUT_LINE('修改后');
Disp_dept_summary();
DELETE FROM emp WHERE empno=9999;
DELETE FROM dept WHERE deptno=90;
DBMS_OUTPUT.PUT_LINE('删除后');
Disp_dept_summary();
DBMS_UTILITY.EXEC_DDL_STATEMENT(‘DROP TRIGGER trig1’);
EXCEPTION
WHEN OTHERS THEN
DBMS_OUTPUT.PUT_LINE(SQLCODE||'---'||SQLERRM);
END;
例2：创建DML语句行级触发器。当对emp表执行INSERT, UPDATE, DELETE 操作时，它自动更新dept_summary 表中的数据。由于在PL/SQL块中不能直接调用DDL语句，所以，利用ORACLE内置包DBMS_UTILITY中的EXEC_DDL_STATEMENT过程，由它执行DDL语句创建触发器。
BEGIN
DBMS_OUTPUT.PUT_LINE('插入前');
Disp_dept_summary();
DBMS_UTILITY.EXEC_DDL_STATEMENT(
'CREATE OR REPLACE TRIGGER trig2_update
AFTER UPDATE OF sal ON emp
REFERENCING OLD AS old_emp NEW AS new_emp
FOR EACH ROW
WHEN (old_emp.sal != new_emp.sal)
BEGIN
DBMS_OUTPUT.PUT_LINE(''正在执行trig2_update 触发器…'');
DBMS_OUTPUT.PUT_LINE(''sal 旧值：''|| :old_emp.sal);
DBMS_OUTPUT.PUT_LINE(''sal 新值：''|| :new_emp.sal);
UPDATE dept_summary
SET sal_sum=sal_sum + :new_emp.sal - :old_emp.sal
WHERE deptno = :new_emp.deptno;
END;'
);
DBMS_UTILITY.EXEC_DDL_STATEMENT(
'CREATE OR REPLACE TRIGGER trig2_insert
AFTER INSERT ON emp
REFERENCING NEW AS new_emp
FOR EACH ROW
DECLARE
I NUMBER;
BEGIN
DBMS_OUTPUT.PUT_LINE(''正在执行trig2_insert 触发器…'');
SELECT COUNT(*) INTO I
FROM dept_summary WHERE deptno = :new_emp.deptno;
IF I > 0 THEN
UPDATE dept_summary
SET sal_sum=sal_sum+:new_emp.sal,
Emp_count=emp_count+1
WHERE deptno = :new_emp.deptno;
ELSE
INSERT INTO dept_summary
VALUES (:new_emp.deptno, :new_emp.sal, 1);
END IF;
END;'
);
DBMS_UTILITY.EXEC_DDL_STATEMENT(
'CREATE OR REPLACE TRIGGER trig2_delete
AFTER DELETE ON emp
REFERENCING OLD AS old_emp
FOR EACH ROW
DECLARE
I NUMBER;
BEGIN
DBMS_OUTPUT.PUT_LINE(''正在执行trig2_delete 触发器…'');
SELECT emp_count INTO I
FROM dept_summary WHERE deptno = :old_emp.deptno;
IF I >1 THEN
UPDATE dept_summary
SET sal_sum=sal_sum - :old_emp.sal,
Emp_count=emp_count - 1
WHERE deptno = :old_emp.deptno;
ELSE
DELETE FROM dept_summary WHERE deptno = :old_emp.deptno;
END IF;
END;'
);
INSERT INTO dept(deptno, dname, loc)
VALUES(90, 'demo_dept', 'none_loc');
INSERT INTO emp(ename, deptno, empno, sal)
VALUES(USER, 90, 9999, 3000);
INSERT INTO emp(ename, deptno, empno, sal)
VALUES(USER, 90, 9998, 2000);
DBMS_OUTPUT.PUT_LINE('插入后');
Disp_dept_summary();
UPDATE emp SET sal = sal*1.1 WHERE deptno=90;
DBMS_OUTPUT.PUT_LINE('修改后');
Disp_dept_summary();
DELETE FROM emp WHERE deptno=90;
DELETE FROM dept WHERE deptno=90;
DBMS_OUTPUT.PUT_LINE('删除后');
Disp_dept_summary();
DBMS_UTILITY.EXEC_DDL_STATEMENT('DROP TRIGGER trig2_update');
DBMS_UTILITY.EXEC_DDL_STATEMENT('DROP TRIGGER trig2_insert');
DBMS_UTILITY.EXEC_DDL_STATEMENT('DROP TRIGGER trig2_delete');
EXCEPTION
WHEN OTHERS THEN
DBMS_OUTPUT.PUT_LINE(SQLCODE||'---'||SQLERRM);
END;
DBMS_OUTPUT.PUT_LINE('插入前');
Disp_dept_summary();
DBMS_UTILITY.EXEC_DDL_STATEMENT(
'CREATE OR REPLACE TRIGGER trig2_update
AFTER UPDATE OF sal ON emp
REFERENCING OLD AS old_emp NEW AS new_emp
FOR EACH ROW
WHEN (old_emp.sal != new_emp.sal)
BEGIN
DBMS_OUTPUT.PUT_LINE(''正在执行trig2_update 触发器…'');
DBMS_OUTPUT.PUT_LINE(''sal 旧值：''|| :old_emp.sal);
DBMS_OUTPUT.PUT_LINE(''sal 新值：''|| :new_emp.sal);
UPDATE dept_summary
SET sal_sum=sal_sum + :new_emp.sal - :old_emp.sal
WHERE deptno = :new_emp.deptno;
END;'
);
DBMS_UTILITY.EXEC_DDL_STATEMENT(
'CREATE OR REPLACE TRIGGER trig2_insert
AFTER INSERT ON emp
REFERENCING NEW AS new_emp
FOR EACH ROW
DECLARE
I NUMBER;
BEGIN
DBMS_OUTPUT.PUT_LINE(''正在执行trig2_insert 触发器…'');
SELECT COUNT(*) INTO I
FROM dept_summary WHERE deptno = :new_emp.deptno;
IF I > 0 THEN
UPDATE dept_summary
SET sal_sum=sal_sum+:new_emp.sal,
Emp_count=emp_count+1
WHERE deptno = :new_emp.deptno;
ELSE
INSERT INTO dept_summary
VALUES (:new_emp.deptno, :new_emp.sal, 1);
END IF;
END;'
);
DBMS_UTILITY.EXEC_DDL_STATEMENT(
'CREATE OR REPLACE TRIGGER trig2_delete
AFTER DELETE ON emp
REFERENCING OLD AS old_emp
FOR EACH ROW
DECLARE
I NUMBER;
BEGIN
DBMS_OUTPUT.PUT_LINE(''正在执行trig2_delete 触发器…'');
SELECT emp_count INTO I
FROM dept_summary WHERE deptno = :old_emp.deptno;
IF I >1 THEN
UPDATE dept_summary
SET sal_sum=sal_sum - :old_emp.sal,
Emp_count=emp_count - 1
WHERE deptno = :old_emp.deptno;
ELSE
DELETE FROM dept_summary WHERE deptno = :old_emp.deptno;
END IF;
END;'
);
INSERT INTO dept(deptno, dname, loc)
VALUES(90, 'demo_dept', 'none_loc');
INSERT INTO emp(ename, deptno, empno, sal)
VALUES(USER, 90, 9999, 3000);
INSERT INTO emp(ename, deptno, empno, sal)
VALUES(USER, 90, 9998, 2000);
DBMS_OUTPUT.PUT_LINE('插入后');
Disp_dept_summary();
UPDATE emp SET sal = sal*1.1 WHERE deptno=90;
DBMS_OUTPUT.PUT_LINE('修改后');
Disp_dept_summary();
DELETE FROM emp WHERE deptno=90;
DELETE FROM dept WHERE deptno=90;
DBMS_OUTPUT.PUT_LINE('删除后');
Disp_dept_summary();
DBMS_UTILITY.EXEC_DDL_STATEMENT('DROP TRIGGER trig2_update');
DBMS_UTILITY.EXEC_DDL_STATEMENT('DROP TRIGGER trig2_insert');
DBMS_UTILITY.EXEC_DDL_STATEMENT('DROP TRIGGER trig2_delete');
EXCEPTION
WHEN OTHERS THEN
DBMS_OUTPUT.PUT_LINE(SQLCODE||'---'||SQLERRM);
END;
