oracle 触发器

创建触发器

--before 触发器
create or replace trigger tr_src_emp
before insert or update or delete on emp
declare
begin
end;

--after 行触发器
例如：统计员工工资变化
create table emp_change(
name varchar2(10),
oldsal number(6,2),
newsal number(6,2),
time date);
--
create or replace trigger tr_sal_sal
after update of sal on emp
for each row
declare
v_temp int;
begin
select count(*) into v_temp from emp_change where name =:old.ename;
if v_tem = 0 then
insert into emp_change values(:old.ename,:old.sal,:new.sal,:sysdate);
else
update emp_change set oldsal=:old.sal,newsal=:new.sal,time=sysdate
where name=:old.ename;
end if;
end;
/

触发器的用途
1 控制数据安全
例如：在非工作时间不能对emp表做操作

create or replace trigger tr_emp_time
before insert or update or delete on emp
begin
if to_char(sysdate,'HH24') not betwenn '9' add '17' then
raise_application_error(-20101,'not work time');
end if;
end;
/