Which Entrant has a vanwall straight-4 engine?
CREATE TABLE "complete_world_championship_grand_prix_r" (
  "year" real,
  "entrant" text,
  "chassis" text,
  "engine" text,
  "points" real
);
SELECT "entrant" FROM "complete_world_championship_grand_prix_r" WHERE "engine"='vanwall straight-4';