instruction: Number of distinct users who posted a question, in the last year (365 days). Number of distinct users who posted a Q or an A, in the last 30 days
response: SELECT COUNT(DISTINCT Users.Id) FROM Users JOIN Posts ON Posts.OwnerUserId = Users.Id AND (Posts.PostTypeId = 2) WHERE DATEDIFF(day, Posts.CreationDate, GETDATE()) < 365