For all countries with 7 bronze medals and a total number of medals less than 13, what's the sum of silver medals?
CREATE TABLE "medal_table" (
  "rank" text,
  "nation" text,
  "gold" real,
  "silver" real,
  "bronze" real,
  "total" real
);
SELECT SUM("silver") FROM "medal_table" WHERE "bronze"=7 AND "total"<13;