oracle级联删除

create table dpt(

dptno number(10) not null,

dptname varchar2(30) not null,

constraint pk_dpt primary key(dptno)

)

create table ep(

epno number(10) not null,

epname varchar2(30),

ep_dptno number(10),

constraint pk_ep primary key(epno)

);

方法一：on delete cascade

alter table ep

add constraint fk_ep foreign key(ep_dptno) references dpt(dptno)

on delete cascade;

insert into dpt values(1,'销售部');

insert into dpt values(2,'财务部');

insert into ep values(2,'Mary',1);

insert into ep values(3,'Linda',2);

insert into ep values(4,'Linlin',1);

delete from dpt where dptno=1;

方法二：on delete set null

//alter table ep drop constraint fk_ep(约束名) cascade;#删除约束

alter table ep

add constraint fk_ep foreign key(ep_dptno) references dpt(dptno)

on delete set null

insert into dpt values(1,'销售部');

insert into dpt values(2,'财务部');

insert into ep values(2,'Mary',1);

insert into ep values(3,'Linda',2);

insert into ep values(4,'Linlin',1);

delete from dpt where dptno=1;

方法三：使用触发器

create or replace trigger dpt_ep

before

delete on dpt for each row

begin

delete from ep where ep.ep_dptno=:old.dptno;

end