What is the score for set 2 when set 3 was 15–6?
CREATE TABLE "pool_e" (
  "date" text,
  "score" text,
  "set_1" text,
  "set_2" text,
  "set_3" text,
  "total" text
);
SELECT "set_2" FROM "pool_e" WHERE "set_3"='15–6';