how many winners were in round 8
CREATE TABLE "full_series_results" (
  "rd" real,
  "race" text,
  "pole_position" text,
  "fastest_lap" text,
  "winning_driver" text,
  "winning_team" text,
  "report" text
);
SELECT COUNT("winning_driver") FROM "full_series_results" WHERE "rd"=8;