级联更新、级联删除是指在建立主外键关系的时候设定的一个选项
主要是主表里数据发生变化时从表也跟着变化,但是只有更新和删除,没有插入
你可以在企业管理器里做,也可以写SQL 语句
alter table score
add constraint fk_score_xh foreign key(xh) references student(xh)
on update cascade on delete cascade
主要是主表里数据发生变化时从表也跟着变化,但是只有更新和删除,没有插入
你可以在企业管理器里做,也可以写SQL 语句
alter table score
add constraint fk_score_xh foreign key(xh) references student(xh)
on update cascade on delete cascade
add constraint fk_sales_customerID foreign key(customerID) references bcustomer(customerID)
on update cascade on delete cascade
drop constraint constraintname
go
alter table sales
add constraint fk_bc
foreign key(customerID)
references bcustomer(customerid)
on update cascade
alter table sales
drop constraint constraintname
go
alter table sales
add constraint fk_bc
foreign key(customerID)
references bcustomer(customerid)
on update cascade on delete cascade