How many episodes had 11.47 million viewers? 
CREATE TABLE "u_s_nielsen_ratings" (
  "episode" real,
  "first_air_date" text,
  "rating_18_49" text,
  "share_18_49" real,
  "viewers_millions" text,
  "rank_timeslot" text,
  "rank_night" text
);
SELECT COUNT("episode") FROM "u_s_nielsen_ratings" WHERE "viewers_millions"='11.47';