Which race had a distance of 4 miles where the runner-up was not known?
CREATE TABLE "summary" (
  "race_name" text,
  "dist_miles" text,
  "course" text,
  "prize" text,
  "odds" text,
  "runners" real,
  "place" real,
  "runner_up" text
);
SELECT "race_name" FROM "summary" WHERE "dist_miles"='4' AND "runner_up"='not known';