title: Is there a simple way to create a unique integer key from a two-integer composite key?
body: <p>For various reasons that aren't too germane to the question, I've got a table with a composite key made out of two integers and I want to create a single unique key out of those two numbers. My initial thought was to just concatenate them, but I ran into a problem quickly when I realized that a composite key of (51,1) would result in the same unique key as (5,11), namely, 511. </p>
  
  <p>Does anyone have a clever way to generate an integer out of two integers such that the generated integer is unique to the pair of start integers?</p>
  
  <p><strong>Edit:</strong> After being confronted with an impressive amount of math, I'm realizing that one detail I should have included is the sizes of the keys in question. In the originating pair, the first key is currently 6 digits and will probably stay in 7 digits for the life of the system; the second key has yet to get larger than 20. Given these constraints, it looks like the problem is much less daunting.</p>