คำถามและคำตอบต่อวัน ไม่จำเป็นต้องใช้ทุกตาราง
Questions and answers per day.It is not neccessary to use all the tables.
 PostLinks:  Id [ number]  CreationDate [ time]  PostId [ number]  RelatedPostId [ number]  LinkTypeId [ number] 
SELECT DAY(CreationDate) AS creationDay, MONTH(CreationDate) AS creationMonth, (CASE WHEN ParentId IS NULL THEN 1 ELSE 0 END) AS isAnswer, COUNT(Id) AS cnt FROM Posts WHERE YEAR(Posts.CreationDate) = 2019 AND Posts.DeletionDate IS NULL GROUP BY DAY(CreationDate), MONTH(CreationDate), (CASE WHEN ParentId IS NULL THEN 1 ELSE 0 END)