CREATE TABLE table_203_231 (id DECIMAL, "season" TEXT, "tier" DECIMAL, "division" TEXT, "place" TEXT)

which tier was ud alzira a part of the least ?
SELECT "tier" FROM table_203_231 GROUP BY "tier" ORDER BY COUNT(*) LIMIT 1
SELECT "tier" FROM "table_203_231" GROUP BY "tier" ORDER BY COUNT(*) NULLS FIRST LIMIT 1