Which Capacity is the lowest one that has a City of brisbane, and a Rank smaller than 1?
CREATE TABLE "davis_cup_and_federation_cup_venues" (
  "rank" real,
  "stadium" text,
  "capacity" real,
  "city" text,
  "country" text
);
SELECT MIN("capacity") FROM "davis_cup_and_federation_cup_venues" WHERE "city"='brisbane' AND "rank"<1;