จำนวนผู้ใช้ใหม่ต่อวันในสัปดาห์..ไม่จำเป็นต้องใช้ทุกตาราง
Number of new Users per weekday..It is not neccessary to use all the tables.
 Users:  Id [ number]  Reputation [ number]  CreationDate [ time]  DisplayName [ text]  LastAccessDate [ time]  WebsiteUrl [ text]  Location [ text]  AboutMe [ text]  Views [ number]  UpVotes [ number]  DownVotes [ number]  ProfileImageUrl [ text]  EmailHash [ text]  AccountId [ number] 
SELECT TIME_TO_STR(CreationDate, '%W') AS "day_of_week", COUNT(*) AS "number_of_new_users" FROM Users GROUP BY TIME_TO_STR(CreationDate, '%W') ORDER BY 'day_of_week'