What is the mean number of totals with no silvers and a bronze number less than 0?
CREATE TABLE "medal_count" (
  "rank" real,
  "nation" text,
  "gold" real,
  "silver" real,
  "bronze" real,
  "total" real
);
SELECT AVG("total") FROM "medal_count" WHERE "silver"=0 AND "bronze"<0;