What Aggregate has a 2-1 1st leg, and is from Belgrano?
CREATE TABLE "losers_knockout" (
  "home_1st_leg" text,
  "home_2nd_leg" text,
  "1st_leg" text,
  "2nd_leg" text,
  "aggregate" text
);
SELECT "aggregate" FROM "losers_knockout" WHERE "1st_leg"='2-1' AND "home_1st_leg"='belgrano';