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

Use this type of query: SQL Server
(You can change id of ORDER BY id to each column that you want it)

SELECT 
    p.id, 
    p.person_name, 
    d.department_name, 
    c.phone_number
FROM
    person p
    LEFT JOIN 
    (SELECT *, ROW_NUMBER() OVER (PARTITION BY person_id ORDER BY id) AS seq
     FROM department) d 
    ON d.person_id = p.id And d.seq = 1
    LEFT JOIN 
    ( SELECT *, ROW_NUMBER() OVER (PARTITION BY person_id ORDER BY id) AS seq
     FROM contact) c 
    ON c.person_id = p.id And c.seq = 1;