Q&A for professionals in medical and allied health fields, students of those professions, related academics, and others with a sound understanding of medicine and healthcare-related sciences
SELECT date1, AVG(diff1) as cnt FROM ( SELECT DATEDIFF(day, d.CreationDate, d.ClosedDate) as [diff1], FORMAT (d.CreationDate, 'yy-MM') as [date1], FORMAT (d.ClosedDate, 'yy-MM') as [date2], (d.Id) as id FROM Posts d -- d=duplicate LEFT JOIN PostHistory ph ON ph.PostId = d.Id LEFT JOIN PostLinks pl ON pl.PostId = d.Id LEFT JOIN Posts o ON o.Id = pl.RelatedPostId -- o=original WHERE d.PostTypeId = 1 -- 1=Question AND ph.PostHistoryTypeId = 10 -- 10=Post Closed ) as t1 group by date1 order by date1