link between fnd_user and per_all_people_f

 SELECT
    fur.user_id,
    fur.user_name,
    papf.employee_number,
    papf.full_name
FROM
    per_all_people_f  papf,
    fnd_user          fur
WHERE
        1 = 1
    AND papf.person_id = fur.employee_id
    AND trunc(sysdate) BETWEEN trunc(papf.effective_start_date) AND trunc(papf.effective_end_date)
    AND papf.employee_number = 704391
ORDER BY
    fur.user_id;