What is the smallest rank number of those used to rank the islands? 
CREATE TABLE "islands_over_square_miles_km" (
  "rank" real,
  "islands_name" text,
  "area_sqmi" real,
  "area_km_2" real,
  "location" text,
  "population_2000" text
);
SELECT MIN("rank") FROM "islands_over_square_miles_km";