select
EMP_CODE AS CODE,
EMP_LAST_NAME AS SURNAME,
EMP_FIRST_NAME as NAME
from 
EMP
where
REPLACE(EMP_LAST_NAME,' ','') || REPLACE(EMP_FIRST_NAME,' ','') in(
SELECT REPLACE(EMP_LAST_NAME,' ','') || REPLACE(EMP_FIRST_NAME,' ','')
FROM EMP
GROUP BY REPLACE(EMP_LAST_NAME,' ','') || REPLACE(EMP_FIRST_NAME,' ','')
)
AND
VALID_FLG = '1'
Order By 
REPLACE(EMP_LAST_NAME,' ','') asc,
EMP_CODE asc
limit 4