แผนกใดที่แสดงเพียงครั้งเดียว ?ไม่จำเป็นต้องใช้ตารางทั้งหมด
which division is listed only once ?It is not neccessary to use all the tables.
 table_204_589:  id [ number]  "season" [ text]  "tier" [ number]  "division" [ text]  "pos." [ text]  "notes" [ text] 
SELECT "division" FROM table_204_589 GROUP BY "division" HAVING COUNT(*) = 1