ORACLE触发器类型

1.DML触发器
由对表的INSERT,DELETE,UPDATE激发

CREATE OR REPLACE TRIGGER trigger_name
AFTER                                    -- TIMING :BEFORE OR AFTER
DELETE OR INSERT OR UPDATE ON table_name -- STATEMENT
--REFERENCING :new a :old b              -- new，语句后的表，old，语句前的表
FOR EACH ROW                             -- LEVEL，行级
BEGIN
     --PL/SQL 
     IF INSERTING THEN
         insert into AUDIT_STUDENT
         values
         (sysdate, :new.id, :new.name, 'INSERT');
     ELSIF DELETING THEN
         insert into AUDIT_STUDENT
         values
         (sysdate, :old.id, :old.name, 'DELETE');
     ELSE
         insert into AUDIT_STUDENT
         values
         (sysdate, :old.id, :old.name, 'UPDATE');
     END IF;
END;
/

/*DML触发器执行顺序
a.BEFORE语句级
b.BEFORE行级
c.AFTER行级
d.AFTER语句级
*/

语句级触发器：在语句执行前或执行后被触发
行级触发器：在每个触发语句影响的行触发一次，

2.INSTEAD OF触发器
代替直接对视图的INSERT,DELETE,UPDATE操作

CREATE OR REPLACE TRIGGER VW_STU_COURSE_INSERT
INSTEAD OF INSERT ON VW_STU_COURSE
FOR EACH ROW
DECLARE
      rowcnt number;
BEGIN
      INSERT INTO stu_info(id,name)
      values(:new.id,:new.name);

      insert into course_info(course_no,course_name)
      values(:new.course_no,:new.course_name);
END;
/

3.系统触发器
a.DDL事件(CREATE,ALTER,DROP语句),需要有ADMISTRATER,DATABASE,TRIGGER特权
b.数据库事件
    服务器启动,关闭
    用户登录,注销
    服务器错误等

CREATE OR REPLACE TRIGGER LogUser2Connects
AFTER LOGON ON DATABASE
BEGIN
      INSERT INTO logon_record
      values(sysdate,ora_login_user);
END;
/

--Enabling And Disabling Triggers
--Enabling Triggers
    ALTER TRIGGER REORDER ENABLE;
    ALTER TABLE INVENTORY ENABLE ALL TRIGGERS;
--Enabling Triggers
    ALTER TRIGGER REORDER DISABLING;
    ALTER TABLE INVENTORY DISABLING ALL TRIGGERS;

--View Of Triggers
USER_TRIGGERS
ALL_TRIGGERS
DBA_TRIGGERS