คะแนนคำตอบเฉลี่ยตลอดหลายปี ไม่จำเป็นต้องใช้ตารางทั้งหมด
Average answers score through years.It is not neccessary to use all the tables.
 PostFeedback:  Id [ number]  PostId [ number]  IsAnonymous [ boolean]  VoteTypeId [ number]  CreationDate [ time] 
SELECT TIME_TO_STR(CreationDate, '%Y') AS "year", AVG(Score) AS "average" FROM Posts WHERE PostTypeId = 2 AND CommunityOwnedDate IS NULL AND ClosedDate IS NULL AND Score > 10 GROUP BY TIME_TO_STR('creationdate', '%Y')