Name the  Silver that has a Total smaller than 2, and a Nation of south korea?
CREATE TABLE "medal_table" (
  "rank" text,
  "nation" text,
  "gold" real,
  "silver" real,
  "bronze" real,
  "total" real
);
SELECT AVG("silver") FROM "medal_table" WHERE "total"<2 AND "nation"='south korea';