Joining INTO many-to-many table (From Primary Key Table) - mysql

Question

This is how far i have gotten, though i don't think it can be done with 1 SQL-statement, i just want to confirm whether or not it is possible to do this with ONLY 1 statement:
SELECT * FROM users
INNER JOIN users_mentors ON users_mentors.id=users.mentoruser_id
INNER JOIN mentor_types ON (mentor_types.id=users_mentors.mentor_type OR users_mentors.mentor_type IS NULL)
INNER JOIN mentor_geographies ON mentor_geographies.mentor_id=users_mentors.id
INNER JOIN communes ON communes.id=mentor_geographies.commune_id
LIMIT 0,10
users table with foreignkey to users_mentors:
+------+---------+---------------+
| id | user_id | mentoruser_id |
+------+---------+---------------+
| 1886 | NULL | 4 |
| 1885 | NULL | NULL |
| 1884 | NULL | NULL |
| 1883 | NULL | NULL |
| 1882 | NULL | NULL |
+------+---------+---------------+
users_mentors table (in a many-to-many relationship with communes):
+----+-------------+
| id | mentor_type |
+----+-------------+
| 4 | NULL |
| 1 | 1 |
| 2 | 2 |
| 3 | 3 |
+----+-------------+
communes table (in a many-to-many relationship with users_mentors):
+----+--------------+-------+----------+
| id | name | short | contract |
+----+--------------+-------+----------+
| 1 | København | NULL | 0 |
| 2 | Aarhus | NULL | 0 |
| 3 | Aalborg | NULL | 0 |
| 4 | Odense | NULL | 0 |
| 5 | Esbjerg | NULL | 0 |
+----+--------------+-------+----------+
mentor_geographies table (the m2m table that has FK to communes & users_mentors):
+----+-----------+------------+
| id | mentor_id | commune_id |
+----+-----------+------------+
| 1 | 4 | 1 |
| 2 | 4 | 2 |
+----+-----------+------------+
Is it possible to get all rows from users_mentors and a list of all their commune.type's, IF THEY EXIST (if mentor_geographies is empty, i want empty list of commune.type). In all cases i want the user.

Answer 1

If you want all users, use left join:
SELECT *
FROM users LEFT JOIN
users_mentors
ON users_mentors.id = users.mentoruser_id LEFT JOIN
mentor_types
ON mentor_types.id=users_mentors.mentor_type OR
users_mentors.mentor_type IS NULL LEFT JOIN
mentor_geographies
ON mentor_geographies.mentor_id = users_mentors.id LEFT JOIN
communes
ON communes.id = mentor_geographies.commune_id
LIMIT 0, 10;
I would also recommend that you use table aliases. They make the queries easier to write and to read:
SELECT *
FROM users u LEFT JOIN
users_mentors um
ON um.id = u.mentoruser_id LEFT JOIN
mentor_types mt
ON mt.id = um.mentor_type OR
um.mentor_type IS NULL LEFT JOIN
mentor_geographies mg
ON mg.mentor_id = um.id LEFT JOIN
communes c
ON c.id = mg.commune_id
LIMIT 0, 10