一个表的列如何设置成另外两个表的外键
一个表的列怎么设置成另外两个表的外键
UserId 回复者Id Varchar(20) 非空 TeacherUsesr表或StudentUsers表的外键
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UserId 回复者Id Varchar(20) 非空 TeacherUsesr表或StudentUsers表的外键
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- SQL code
alter table user add constraint fk_test foreign key(UserId) references TeacherUsesr(UserId) go alter table user add constraint fk_test foreign key(UserId) references StudentUsers(UserId) go