Which Silver is the highest one that has a Rank of 19, and a Gold larger than 0?
CREATE TABLE "invitational_sports" (
  "rank" text,
  "nation" text,
  "gold" real,
  "silver" real,
  "bronze" real,
  "total" real
);
SELECT MAX("silver") FROM "invitational_sports" WHERE "rank"='19' AND "gold">0;