With a Season premiere of 23 july 2008 this show has what as the average episode?
CREATE TABLE "overview" (
  "season" text,
  "episodes" real,
  "season_premiere" text,
  "season_finale" text,
  "peak_series_rating_citation_needed" text,
  "average_series_rating" text,
  "dvd_release_date" text,
  "discs" real
);
SELECT AVG("episodes") FROM "overview" WHERE "season_premiere"='23 july 2008';