Oracle触发器Trigger4触发条件_when的使用

/*

同一表使用所有条件

Create or replace trigger t5 

      Before  insert,delete,update  on 表名

     For each row

    //plsql块



*/

/*

在触发器中，还有三个变量：都是boolean

    INSERTING 正在执行insert吗。

    DELETING

    UPDATING



*/

select TABLE_NAME from USER_TABLES;

select * from trigger_t2;

desc trigger_t2;

create or replace trigger t4

before INSERT OR UPDATE or delete on trigger_t2

  FOR EACH ROW

  declare

  begin

  if inserting then

  dbms_output.put_line('写入');

  elsif deleting then

  dbms_output.put_line('删除');

  else 

  dbms_output.put_line('更新');

end if;

end;

---测试

set serveroutput on;

insert into trigger_t2 values(1,'jk',23);

delete from trigger_t2 where id=1;

update trigger_t2 set name='kk';

---------------------------------------------------

---------------------------------------------------

--使用when语句设置条件

create or replace trigger t5

before INSERT on trigger_t2

  FOR EACH ROW

  when (NEW.age<=18)

  declare

  begin

  DBMS_OUTPUT.PUT_LINE('大于20是：'||:NEW.age);

  RAISE_APPLICATION_ERROR(-20000, '年龄小于18不能参与');

end;

set serveroutput on;

INSERT INTO TRIGGER_T2 VALUES(4,'KK',22);

/*

--禁用trigger

alter trigger t4 disable;

alter trigger t4 enable;

--修改名称

alter trigger t4 rename to t5;

*/