CREATE TABLE table_203_545 (id DECIMAL, "single/ep" TEXT, "release date" TEXT, "label" TEXT, "format ( s ) " TEXT, "uk singles chart position" DECIMAL, "notes" TEXT)

which format was used the most according to this chart ?
SELECT "format(s)" FROM table_203_545 GROUP BY "format(s)" ORDER BY COUNT(*) DESC LIMIT 1
SELECT "format(s)" FROM "table_203_545" GROUP BY "format(s)" ORDER BY COUNT(*) DESC NULLS LAST LIMIT 1