What number episode had a rating of 4.7?
CREATE TABLE "season_1_2010" (
  "no" real,
  "episode" text,
  "rating" text,
  "share" real,
  "rating_share_18_49" text,
  "viewers_millions" text,
  "rank_timeslot" real,
  "rank_night" real
);
SELECT MIN("no") FROM "season_1_2010" WHERE "rating"='4.7';