WITH t AS (
    SELECT
        EMP_CODE AS CODE
        , EMP_LAST_NAME AS SURNAME
        , EMP_FIRST_NAME AS NAME
        , REPLACE(EMP_LAST_NAME || EMP_FIRST_NAME, ' ', '') AS FULL_NAME
    FROM
        EMP
    WHERE
        VALID_FLG = '1'
)

SELECT
    t1.CODE
    , t1.SURNAME
    , t1.NAME
FROM
    t AS t1
INNER JOIN
    t AS t2
ON
    t1.CODE <> t2.CODE
    AND t1.FULL_NAME = t2.FULL_NAME
ORDER BY
    t1.FULL_NAME, t1.CODE
;