DELETE 
FROM ESFRSLN_MIG M 
WHERE M.ROWID IN (  SELECT T1.ROWID
                    FROM ESFRSLN_MIG T1
                    JOIN ESFRSLN_MIG T2 ON  T2.KOR    = T1.KOR
                                        AND T2.ROWID  < T1.ROWID
                    WHERE T1.KOR IN (SELECT KOR 
                                    FROM ESFRSLN_MIG
                                    GROUP BY KOR
                                    HAVING COUNT(*) > 1));
COMMIT;