คิดเป็นรายเดือน ไม่จำเป็นต้องใช้ทุกตาราง
s by month.It is not neccessary to use all the tables.
 ReviewRejectionReasons:  Id [ number]  Name [ text]  Description [ text]  PostTypeId [ number] 
SELECT DATEADD(month, DATEDIFF(month, 0, CreationDate), 0) AS Mnth, (SUM(CASE WHEN Tags LIKE '%dnd%' OR Tags LIKE '%dungeons-and-dragons%' OR Tags LIKE '%pathfinder%' THEN 1 ELSE 0 END) * 100.00) / COUNT(*) AS PercentDND FROM Posts WHERE PostTypeId = 1 GROUP BY DATEADD(month, DATEDIFF(month, 0, CreationDate), 0) ORDER BY DATEADD(month, DATEDIFF(month, 0, CreationDate), 0)