What is the method for a match with a Round larger than 2, he took a loss, and 15–3 was the record?
CREATE TABLE "mixed_martial_arts_record" (
  "res" text,
  "record" text,
  "opponent" text,
  "method" text,
  "event" text,
  "round" real,
  "location" text
);
SELECT "method" FROM "mixed_martial_arts_record" WHERE "round">2 AND "res"='loss' AND "record"='15–3';