CREATE TABLE "winners_knockout" (
  "home_1st_leg" text,
  "home_2nd_leg" text,
  "1st_leg" text,
  "2nd_leg" text,
  "aggregate" text
);

Question: What was the 2nd leg that had a first leg of 1-1?
SQL: SELECT "home_2nd_leg" FROM "winners_knockout" WHERE "1st_leg"='1-1';

Question: What was the first leg home that had a total aggregate of 3-1?
SQL: SELECT "home_1st_leg" FROM "winners_knockout" WHERE "aggregate"='3-1';

Question: What was the 1st leg that had a 4-2 aggregate?
SQL: SELECT "1st_leg" FROM "winners_knockout" WHERE "aggregate"='4-2';

Question: What was the 1st leg that had a 1st get home for the Boca Juniors?
SQL: SELECT "1st_leg" FROM "winners_knockout" WHERE "home_1st_leg"='boca juniors';

Question: What was the 2nd leg that had the Estudiantes La Plata home for the 2nd leg?
SQL: SELECT "2nd_leg" FROM "winners_knockout" WHERE "home_2nd_leg"='estudiantes la plata';