s/answers ด้วยแท็ก ไม่จำเป็นต้องใช้ทุกตาราง
s/answers by tag.It is not neccessary to use all the tables.
 PostLinks:  Id [ number]  CreationDate [ time]  PostId [ number]  RelatedPostId [ number]  LinkTypeId [ number] 
SELECT TagName, COUNT(DISTINCT Posts.Id) AS "Number of questions", (SELECT SUM(Score) FROM Tags AS TagsI INNER JOIN PostTags ON PostTags.TagId = TagsI.Id INNER JOIN Posts ON PostTags.PostId = Posts.Id WHERE TagsI.TagName = TagsO.TagName) AS "Total score of all questions", COUNT(Answers.Id) AS "Number of answers", SUM(Answers.Score) AS "Total score of all answers" FROM Tags AS TagsO INNER JOIN PostTags ON PostTags.TagId = TagsO.Id INNER JOIN Posts ON PostTags.PostId = Posts.Id LEFT JOIN Posts AS Answers ON Posts.Id = Answers.ParentId GROUP BY TagName