[RESOLVED] How do you get a unique ID from two numbers w/o ordering them?

[joshstrike]

I think... if I didn't need f(x,y) == f(y,x), and assuming only positive integers where x != y, I could generate a unique number for each pair by doing (x*y)+y ...which gives a hyperbolic paraboloid.
However, that is dependent on the order f(x,y) and doesn't help my situation because I need a key by which to group both ways.

I've gone ahead and solved my problem by using CONCAT(MIN(userID),',',MAX(userID)) to generate a unique identifier, but unfortunately this is rather slow.

[realMakc]

I could generate a unique number for each pair by doing (x*y)+y

suppose you have some z = (x*y)+y. then, for some x1 != x you can find y1 = z / (x1 + 1), so that x1*y1 + y1 is the same z.