What round was a loss with a record of 12-3?
CREATE TABLE "mixed_martial_arts_record" (
  "res" text,
  "record" text,
  "opponent" text,
  "method" text,
  "event" text,
  "round" text
);
SELECT "round" FROM "mixed_martial_arts_record" WHERE "res"='loss' AND "record"='12-3';