?

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;

?

?

例3：利用ORACLE提供的条件谓词INSERTING、UPDATING和DELETING创建与例2具有相同功能的触发器。