ผู้เล่นสัญชาติใด Brian Wilks?ไม่จำเป็นต้องใช้ตารางทั้งหมด
Which nationality is player Brian Wilks?It is not neccessary to use all the tables.
 table_21721351_18:  (nationality [ VARCHAR ] player [ VARCHAR) ]
SELECT nationality FROM table_21721351_18 WHERE player = "Brian Wilks"