触发器的设计删除了的数据，只要没有执行commit，使用rollback可以恢复事务简述什么是事务事务是数据库中重要的机制，用于确保数据完整性和并发处理的能力。它将一条/一组SQL语
句当作成一个逻辑上的单元，用于保障这些语句都成功/失败。事务的特性事务具有ACID四大特性A（Atomicity):原子性C(Consistency):一致性I(Isolation):隔离性D(Durability):永久性
直接登录 sqlplus "/ as sysdba"
不允许对方修改 select * from e for update;update e set sex='女' where eid=1;commit;
例子1：删除create or replace trigger del_didafter delete on dfor each rowbegindelete from e where id=:old.id;end del_did;/执行删除delete from d where id=1;
删除触发器 drop tigger del_id;
例子2：添加create or replace trigger insert_dafter insert on dfor each rowbegininsert into e(eid,ename,sex,id) values('3','赵3','男','3');end;/执行添加insert into d values('3','学生');
例子3：create or replace trigger update_dafter update on dfor each rowbeginupdate e set id:=new.id where id=:old.id;end;/执行更新update d set id='4' where id=1;
例子4：设定不能删除raise_application_errorcreate or replace trigger d_idafter update on dfor each rowbeginif :old.id=1 thenraise_application_error(-20000,'不允许删除！');end if;end;/
例子4:语句型触发器实现操作记录
create table aa(a1 char(100),a2 char(100),a3 char(100)); insert into aa values('aa','123','dd'); create table mylog(curr_user varchar2(100),curr_date date,act char(1));
create or replace trigger dml_aaafter insert or delete or update on aabeginif inserting theninsert into mylog values(user,sysdate,'I');elseif deleting theninsert into mylog values(user,sysdate,'D');elseinsert into mylog values(user,sysdate,'U');end if;end;/
例子5:
create table auto(a char(10),b char(10)); insert into auto values('1','aaa');
create or replace trigger set_nobefore insert no autofor each rowdeclaresn number(5);beginselect myseq.nextval into sn from dual;:new.a:sn;end;/
例子6：替换触发器create or replace trigger tr_v_e_dinstead of insert on v_emp_dept //v_emp_dept视图for each rowbegininsert into d values(:new.id,:new.name);insert into e(eid,ename,sex,id) values(:new.eid,:new.ename,:new.sex;new.id);end;/
