CREATE TABLE table_203_102 (id DECIMAL, "event" TEXT, "performance" TEXT, "athlete" TEXT, "nation" TEXT, "place" TEXT, "date" TEXT)

which record is faster , 50km race walk or marathon
SELECT "event" FROM table_203_102 WHERE "event" IN ('50 km race walk', 'marathon') ORDER BY "performance" LIMIT 1
SELECT "event" FROM "table_203_102" WHERE "event" IN ('50 km race walk', 'marathon') ORDER BY "performance" NULLS FIRST LIMIT 1