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IdVarchar（20)非空TeacherUsesr表或StudentUsers表的外键

[解决办法]

SQL code

alter table useradd constraint fk_test foreign key(UserId)references TeacherUsesr(UserId)goalter table useradd constraint fk_test foreign key(UserId)references StudentUsers(UserId)go