Q&A for teachers and students of the Esperanto language
SELECT Month = DATEADD(MONTH, DATEDIFF(MONTH, 0, Posts.CreationDate), 0), 'Active users' = COUNT(distinct OwnerUserId) FROM Posts INNER JOIN Users ON Posts.OwnerUserId = Users.Id GROUP BY DATEADD(MONTH, DATEDIFF(MONTH, 0, Posts.CreationDate), 0) ORDER BY Month