Q&A for professional and enthusiast programmers
SELECT DisplayName FROM Users JOIN (SELECT top 1000 OwnerUserId FROM Posts JOIN ( SELECT '2010' beg , '2011' en) b1 ON CreationDate BETWEEN beg AND en INTERSECT SELECT top 1000 OwnerUserId FROM Posts JOIN ( SELECT '2015' beg, '2016' en) b2 ON CreationDate BETWEEN beg AND en) a ON Users.Id = a.OwnerUserId