How many points have 500cc for the class, a win greater than 0, with a year after 1974?
CREATE TABLE "grand_prix_motorcycle_racing_results" (
  "year" real,
  "class" text,
  "team" text,
  "points" real,
  "wins" real
);
SELECT SUM("points") FROM "grand_prix_motorcycle_racing_results" WHERE "class"='500cc' AND "wins">0 AND "year">1974;