What is the smallest number of silvers associated with bronzes under 20, totals of 1, golds of 0, and in Water Polo?
CREATE TABLE "by_sport" (
  "sport" text,
  "gold" real,
  "silver" real,
  "bronze" real,
  "total" real
);
SELECT MIN("silver") FROM "by_sport" WHERE "bronze"<20 AND "total"=1 AND "sport"='water polo' AND "gold"<0;