先用的联合主键
alter table project add constraint pk_project primary key (p_id,PID);
然后在新建表中就无法使用其做外键了T^T
我写的是
create table relation(projectp_id int(20),projectPID int(20), foreign key(projectp_id,projectPID) references project(p_id,PID));
然后就会报错。。。cannot add foreign key constraint
why??????????????
求教!!!!!!!!!!!