Sure there is. You define a before trigger(s) that raise an error if you try to insert or update records such that the constraint is violated. It would not be very efficient, but it would work. However you still have to know *HOW* you define something as being valid or invalid, and we don't know that yet. Because by some magical method undisclosed there are "exclusions" at work that are not yet described (what is the mechanism by which we know that 17 3 is an invalid combination, in the example given, for example -- is it because it is a primary number? But 2 is a primary number. Is it because it is an odd number? If there were a topic 5, would that be permitted or denied? Why or why not?).