What if you have more then one foreign key referencing the same table? Or worse, what if you had one and later add another? You would get undefined behavior. A

What if you have more then one foreign key referencing the same table? Or worse, what if you had one and later add another? You would get undefined behavior. Added: Also SQL language itself has nothing to do with keys, relationships and other details of database design. It's different level of abstraction. Various query builders/SQL generators do what you want.