--实例2------------------------
--创建触发器，它将映射emp表中每个部门的总人数和总工资
--创建映射表
CREATE TABLE dept_sal
?AS
?SELECT deptno,COUNT(empno) AS total_emp,SUM(sal) AS total_sal FROM emp GROUP BY deptno;
DESC dept_sal;
--创建触发器
CREATE OR REPLACE TRIGGER emp_info
AFTER INSERT OR UPDATE OR DELETE ON emp
DECLARE
?CURSOR cur_emp IS
?? SELECT deptno,COUNT(empno) AS total_emp,SUM(sal) AS total_sal FROM emp GROUP BY deptno;
BEGIN
?DELETE dept_sal;? --触发时首先删除映射表信息
?FOR v_emp IN cur_emp LOOP
??--DBMS_OUTPUT.PUT_LINE(v_emp.deptno || v_emp.total_emp || v_emp.total_sal);
??--插入数据
??INSERT INTO dept_sal
???VALUES(v_emp.deptno,v_emp.total_emp,v_emp.total_sal);
?END LOOP;
END;
/
--对emp表进行DML操作
INSERT INTO emp(empno,deptno,sal) VALUES('123','10',10000);
SELECT * FROM dept_sal;
DELETE EMP WHERE empno=123;
SELECT * FROM dept_sal;

--实例3------------------------
--创建触发器，它记录表的删除数据
--创建表
CREATE TABLE employee
(
?id?? VARCHAR2(4)? NOT NULL,
?name VARCHAR2(15) NOT NULL,
?age? NUMBER(2)??? NOT NULL,
?sex? CHAR???????? NOT NULL
);
DESC employee;
--插入数据
INSERT INTO employee VALUES('e101','zhao',23,'M');
INSERT INTO employee VALUES('e102','jian',21,'F');
--创建记录表
CREATE TABLE old_employee AS
?SELECT * FROM employee;
DESC old_employee;
--创建触发器
CREATE OR REPLACE TRIGGER tig_old_emp
AFTER DELETE ON employee? --
FOR EACH ROW? --语句级触发，即每一行触发一次
BEGIN
?INSERT INTO old_employee
??VALUES(:old.id,:old.name,:old.age,:old.sex);? --:old代表旧值
END;
/
--下面进行测试
DELETE employee;
SELECT * FROM old_employee;

--实例4------------------------
--创建触发器，利用视图插入数据
--创建表
CREATE TABLE tab1 (tid NUMBER(4) PRIMARY KEY,tname VARCHAR2(20),tage NUMBER(2));
CREATE TABLE tab2 (tid NUMBER(4),ttel VARCHAR2(15),tadr VARCHAR2(30));
--插入数据
INSERT INTO tab1 VALUES(101,'zhao',22);
INSERT INTO tab1 VALUES(102,'yang',20);
INSERT INTO tab2 VALUES(101,'13761512841','AnHuiSuZhou');
INSERT INTO tab2 VALUES(102,'13563258514','AnHuiSuZhou');
--创建视图连接两张表
CREATE VIEW tab_view AS
?SELECT tab1.tid,tname,ttel,tadr FROM tab1,tab2
??WHERE tab1.tid = tab2.tid;
--创建触发器
CREATE OR REPLACE TRIGGER tab_trigger
INSTEAD OF INSERT ON tab_view
BEGIN
?INSERT INTO tab1(tid,tname) VALUES(:new.tid,:new.tname);
?INSERT INTO tab2(ttel,tadr) VALUES(:new.ttel,:new.tadr);
END;
/
--现在就可以利用视图插入数据
INSERT INTO tab_view VALUES(105,'zhaoyang','13886681288','beijing');
--查看效果
SELECT * FROM tab_view;

--实例5------------------------
--创建触发器，比较emp表中更新的工资
CREATE OR REPLACE TRIGGER sal_emp
BEFORE UPDATE ON emp
FOR EACH ROW
BEGIN
?
?IF :OLD.sal > :NEW.sal THEN
??DBMS_OUTPUT.PUT_LINE('工资减少');
?ELSIF :OLD.sal < :NEW.sal THEN
??DBMS_OUTPUT.PUT_LINE('工资增加');
?ELSE
??DBMS_OUTPUT.PUT_LINE('工资未作任何变动');
?END IF;
?DBMS_OUTPUT.PUT_LINE('更新前工资 ：' || :OLD.sal);
?DBMS_OUTPUT.PUT_LINE('更新后工资 ：' || :NEW.sal);
END;
/
--执行UPDATE查看效果
UPDATE emp SET