How to make such connection in sql?

Question

SQL

How is it possible to link tables so that, for example, C.id is equal to either A.id or B.id , moreover, A.id does not match B.id
Of course, I know about triggers, but I wanted to do without them....

Answer 1

Without them, in this particular case, nothing. You can't create a constraint with this kind of logic.

Answer 2

According to the mind, for this you should make a third table in which all A.id and B.id will be entered. Or take such a restriction to a higher level of logic, or in software, or in a trigger.