CREATE TABLE "2010_11_season_as_a_four_year_old" (
  "result" text,
  "date" text,
  "race" text,
  "venue" text,
  "group" text,
  "distance" text,
  "weight_kg" text,
  "jockey" text,
  "winner_2nd" text
);

Question: The MacKinnon Stakes races took place on how many venues?
SQL: SELECT COUNT("venue") FROM "2010_11_season_as_a_four_year_old" WHERE "race"='Mackinnon Stakes';