สำหรับแท็ก?.ไม่จำเป็นต้องใช้ตารางทั้งหมด
for a tag?.It is not neccessary to use all the tables.
 PostLinks:  Id [ number]  CreationDate [ time]  PostId [ number]  RelatedPostId [ number]  LinkTypeId [ number] 
SELECT COUNT(DISTINCT p.OwnerUserId) FROM Posts AS p INNER JOIN PostTags AS pt ON pt.TagId = @TagId WHERE pt.PostId = p.Id AND p.PostTypeId = 1