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