Q&A for those interested in the geology, meteorology, oceanography, and environmental sciences
SELECT P.OwnerUserId, COALESCE(P.OwnerDisplayName, U.DisplayName) AS DisplayName, COUNT(P.Id) AS Number_of_posts FROM Posts P LEFT JOIN Users U ON P.OwnerUserID = U.Id GROUP BY P.OwnerUserId, COALESCE(P.OwnerDisplayName, U.DisplayName) ORDER BY Number_of_posts DESC OFFSET 0 ROWS FETCH NEXT 15 ROWS ONLY;