Sure. NP-completeness is utterly a matter of theory, I make no claims otherwise. SAT solving is such a powerful tool precisely because you can do so well on "sm

Sure. NP-completeness is utterly a matter of theory, I make no claims otherwise. SAT solving is such a powerful tool precisely because you can do so well on "small" (and often "average") solutions that it's an attractive target for practical instances of other problems -- despite its theoretical NP-completness. The poster I originally responded to was curious about the speed with which 9x9 Sudoku can be solved despite "its" NP-completeness, and my point was that it's because of the small restriction of the general, truly NP-complete problem, and not because of anything inherently special about the SQL-based solver.