WITH EMP1 AS (
SELECT 
    EMP_CODE AS CODE,
    REPLACE(EMP_LAST_NAME," ","") AS SURNAME,
    REPLACE(EMP_FIRST_NAME," ","") AS NAME
FROM EMP
WHERE VALID_FLG = '1'
)
,EMP2 AS (
SELECT
    EMP1.*,
    SURNAME || NAME AS LF_NAME
FROM EMP1
)
SELECT
    T1.CODE,
    T1.SURNAME,
    T1.NAME
FROM EMP2 AS T1
    FULL OUTER JOIN EMP2 AS T2 ON T1.LF_NAME = T2.LF_NAME
    GROUP BY 1,2,3
ORDER BY
    T1.LF_NAME,
    T1.CODE
;