If we define active as writing a question or an answer. Was the given user active for the last 12 months?
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-- uid: User Id
DECLARE @user INT = ##uid:INT##
IF ( (SELECT TOP 1 DATEDIFF(MONTH,GETDATE(),p.CreationDate) AS 'Date'
FROM Posts p WHERE p.OwnerUserId = @user ORDER BY 'Date' DESC) < -12)