CREATE TABLE table_204_517 (id DECIMAL, "name" TEXT, "date of birth" TEXT, "club" TEXT, "division" TEXT, "appointed" TEXT, "time as manager" TEXT)

which person has been a manager the longest ?
SELECT "name" FROM table_204_517 ORDER BY "time as manager" DESC LIMIT 1
SELECT "name" FROM "table_204_517" ORDER BY "time as manager" DESC NULLS LAST LIMIT 1