WITH cleansed AS (
    SELECT
        EMP_CODE       as CODE
      , EMP_LAST_NAME  as SURNAME
      , EMP_FIRST_NAME as NAME
      , REPLACE(EMP_LAST_NAME , ' ', '') as C_SURNAME
      , REPLACE(EMP_FIRST_NAME, ' ', '') as C_NAME
    FROM
        EMP
    WHERE
        VALID_FLG = '1'
)
SELECT
    c1.CODE    as CODE
  , c1.SURNAME as SURNAME
  , c1.NAME    as NAME
FROM
           cleansed c1
INNER JOIN cleansed c2
        ON c1.C_SURNAME = c2.C_SURNAME
       AND c1.C_NAME    = c2.C_NAME
WHERE
    c1.CODE != c2.CODE
ORDER BY
    c1.C_SURNAME ASC
  , c1.C_NAME    ASC
  , c1.CODE      ASC
;