CREATE TABLE table_203_874 (id DECIMAL, "year" DECIMAL, "competition" TEXT, "venue" TEXT, "position" TEXT, "event" TEXT, "notes" TEXT)

how long did it take to walk 50 km in the 2004 olympic games ?
SELECT "notes" FROM table_203_874 WHERE "event" = '50 km walk' AND "year" = 2004
SELECT "notes" FROM "table_203_874" WHERE "event" = '50 km walk' AND "year" = 2004