CREATE TABLE table_204_174 (id NUMBER, "rank" NUMBER, "name" CLOB, "nationality" CLOB, "result" NUMBER, "notes" CLOB)

which person medaled , but was not from south korea ?
SELECT "name" FROM table_204_174 WHERE "rank" IS NULL AND "nationality" <> 'south korea'
SELECT "name" FROM "table_204_174" WHERE "nationality" <> 'south korea' AND "rank" IS NULL