Jake Ashcraft, a systems engineer at Progressive Software Solutions in Albany, Oregon, contacted me about a problem to which he could find no set-based solution, just a solution that uses cursors and temporary tables. The problem is representative of a larger group of problems that deal with identifying groups of elements, or identifying subsets within sets. Let's look at the problem, then explore four set-based solutions that approach the problem from different angles. Thanks to Dieter Nöth—a true SQL wizard—for providing one of the solutions I present. As always, I encourage you to try your hand at solving the problem before looking at the solutions.