CREATE TABLE table_35870 ("Res." TEXT, "Record" TEXT, "Opponent" TEXT, "Method" TEXT, "Event" TEXT, "Round" TEXT)

What round was a loss with a record of 12-3?
SELECT "Round" FROM table_35870 WHERE "Res." = 'loss' AND "Record" = '12-3'
SELECT "Round" FROM "table_35870" WHERE "Record" = '12-3' AND "Res." = 'loss'