สนามฟุตบอลคว้าแชมป์ได้กี่สมัย?ไม่จำเป็นต้องใช้ตารางทั้งหมด
How many championships were won for arena football?It is not neccessary to use all the tables.
 table_21564794_3:  (championships_in_st_louis [ VARCHAR ] sport [ VARCHAR) ]
SELECT championships_in_st_louis FROM table_21564794_3 WHERE sport = "Arena Football"