SELECT
 E1.EMP_CODE AS CODE
 ,E1.EMP_LAST_NAME AS SURNAME
 ,E1.EMP_FIRST_NAME AS NAME
 FROM
  (SELECT * FROM EMP WHERE VALID_FLG = '1') AS E1
  LEFT OUTER JOIN (SELECT * FROM EMP WHERE VALID_FLG = '1') AS E2 
        ON TRIM(E1.EMP_LAST_NAME) = TRIM(E2.EMP_LAST_NAME)
        AND TRIM(E1.EMP_FIRST_NAME) = TRIM(E2.EMP_FIRST_NAME)
WHERE
 E1.EMP_CODE <> E2.EMP_CODE
ORDER BY
 TRIM(E1.EMP_LAST_NAME)
  ,E1.EMP_CODE
;