Can you tell me the average Total that had the Silver of 0, and the Rank of 6, and the Gold smaller than 0?
CREATE TABLE "medal_table" (
  "rank" text,
  "nation" text,
  "gold" real,
  "silver" real,
  "bronze" real,
  "total" real
);
SELECT AVG("total") FROM "medal_table" WHERE "silver"=0 AND "rank"='6' AND "gold"<0;