If you are satisfied with an approximation of "DISTINCT", there is a facinating probabilistic algorithm by Flajolet and Martin https://en.wikipedia.org/wiki/Fl

If you are satisfied with an approximation of "DISTINCT", there is a facinating probabilistic algorithm by Flajolet and Martin https://en.wikipedia.org/wiki/Flajolet%E2%80%93Martin_algorithm https://en.wikipedia.org/wiki/Flajolet%E2%80%93Martin_algori... which fits on 10 lines and does not require sorting. Improved versions of it are LogLog and HyperLogLog.