CREATE TABLE table_203_491 (id DECIMAL, "year" DECIMAL, "title" TEXT, "us hot 100" DECIMAL, "us modern rock" DECIMAL, "us mainstream rock" DECIMAL, "album" TEXT)

which album had the most singles releases ?
SELECT "album" FROM table_203_491 GROUP BY "album" ORDER BY COUNT("title") DESC LIMIT 1
SELECT "album" FROM "table_203_491" GROUP BY "album" ORDER BY COUNT("title") DESC NULLS LAST LIMIT 1