What is the Set 3 with a Score of 3–1, and has a Set 2 of 13–15?
CREATE TABLE "pool_a" (
  "date" text,
  "score" text,
  "set_1" text,
  "set_2" text,
  "set_3" text,
  "total" text
);
SELECT "set_3" FROM "pool_a" WHERE "score"='3–1' AND "set_2"='13–15';