CREATE TABLE table_203_528 (id DECIMAL, "year" DECIMAL, "political rights" DECIMAL, "civil liberties" DECIMAL, "status" TEXT, "president" TEXT)

who ruled longer , ali saibou or mamadou tandja ?
SELECT "president" FROM table_203_528 WHERE "president" IN ('ali saibou', 'mamadou tandja') GROUP BY "president" ORDER BY COUNT(*) DESC LIMIT 1
SELECT "president" FROM "table_203_528" WHERE "president" IN ('ali saibou', 'mamadou tandja') GROUP BY "president" ORDER BY COUNT(*) DESC NULLS LAST LIMIT 1