What is the sum of the gold medals of the total nation, which has more than 19 silver medals?
CREATE TABLE "medal_table" (
  "rank" text,
  "nation" text,
  "gold" real,
  "silver" real,
  "bronze" real,
  "total" real
);
SELECT SUM("gold") FROM "medal_table" WHERE "nation"='total' AND "silver">19;