CREATE TABLE table_204_589 (id NUMBER, "season" CLOB, "tier" NUMBER, "division" CLOB, "pos." CLOB, "notes" CLOB)

which division is listed only once ?
SELECT "division" FROM table_204_589 GROUP BY "division" HAVING COUNT(*) = 1
SELECT "division" FROM "table_204_589" GROUP BY "division" HAVING COUNT(*) = 1