What is the total number of Distance ( ly ), when Constellation is "Draco"?
CREATE TABLE "targets" (
  "hd_designation" text,
  "constellation" text,
  "distance_ly" real,
  "spectral_type" text,
  "signal_power_k_w" real,
  "date_sent" text,
  "arrival_date" text
);
SELECT COUNT("distance_ly") FROM "targets" WHERE "constellation"='draco';