Prevent duplicate values in LEFT JOIN

Question

I faced a situation where I got duplicate values from LEFT JOIN. I think this might be a desired behavior but unlike from what I want.

I have three tabl

Answer 1

SELECT p.id, p.person_name, d.department_name, c.phone_number 
FROM person p
  LEFT JOIN department d 
    ON p.id = d.person_id
  LEFT JOIN contact c 
    ON p.id = c.person_id 
group by p.id, p.person_name, d.department_name, c.phone_number