SELECT 
    EMP_CODE AS CODE,
    TRIM(EMP_LAST_NAME) AS SURNAME,
    TRIM(EMP_FIRST_NAME) AS NAME
FROM
    (SELECT
        TRIM(EMP_LAST_NAME) AS LAST, 
        TRIM(EMP_FIRST_NAME) AS FIRST,
        COUNT(EMP_LAST_NAME) AS CNT 
    FROM
        EMP
        GROUP BY LAST, FIRST
        ) AS EMP_CNT
        
INNER JOIN 
    EMP
ON
    LAST = SURNAME 
AND
    FIRST = NAME
AND    
    VALID_FLG = '1'
AND 
    CNT > 1
ORDER BY TRIM(SURNAME) ASC, CODE ASC;