instruction: Days to Close a Duplicate Question by Creation Month.
response: SELECT date1 AS creationDate, AVG(diff1) AS avgDaysToClose FROM (SELECT DATEDIFF(day, d.CreationDate, ClosedDate) AS "diff1", FORMAT(d.CreationDate, 'yy-MM') AS "date1", FORMAT(d.ClosedDate, 'yy-MM') AS "date2", (d.Id) AS id FROM Posts AS d LEFT JOIN PostHistory AS ph ON ph.PostId = d.Id LEFT JOIN PostLinks AS pl ON pl.PostId = d.Id LEFT JOIN Posts AS o ON o.Id = pl.RelatedPostId WHERE d.PostTypeId = 1 AND pl.LinkTypeId = 3 AND ph.PostHistoryTypeId = 10) AS t1 GROUP BY date1 ORDER BY date1