CREATE TABLE table_203_409 (id DECIMAL, "rank" DECIMAL, "representative" TEXT, "party" TEXT, "district" TEXT, "seniority date" TEXT, "notes" TEXT)

who is the congressman with the greatest seniority ?
SELECT "representative" FROM table_203_409 ORDER BY "seniority date" LIMIT 1
SELECT "representative" FROM "table_203_409" ORDER BY "seniority date" NULLS FIRST LIMIT 1