Select latest record on many to many relationship

Question

I have a many to many relationship like below. A user can change their role, and I want to get all users with their last role equals to role2 (example).

users

user_id | user_name  | user_password
1       | user1      | *hashed password*
2       | user2      | *hashed password*
3       | user3      | *hashed password*

roles

role_id | role_name | role_description
1       | role1     | *description*
2       | role2     | *description*

user_roles

user_roles_id | user_id | role_id | created_at
1             | 1       | 1       | 2018-04-10 01:01:01
2             | 2       | 2       | 2018-04-10 01:01:02
3             | 3       | 1       | 2018-04-10 01:01:03
4             | 1       | 2       | 2018-04-12 01:01:01
5             | 1       | 1       | 2018-04-13 01:01:02
6             | 2       | 1       | 2018-04-14 01:01:01
7             | 3       | 2       | 2018-04-14 01:01:02
8             | 2       | 2       | 2018-04-15 01:01:01
9             | 1       | 2       | 2018-04-15 01:01:02
10            | 1       | 1       | 2018-04-16 01:01:01

From those tables, I want to get things like

user_id | role_id
2       | 2
3       | 2

But all this time I got

user_id | role_id
1       | 2
2       | 2
3       | 2

user1 should not be there because its last role was role1. So what I'm trying to do is, get users where last role = 2.

Any help would be appreciated! Thanks in advance!

Addition

The results that I wanted is all data from users table. So it might be like

user_id | user_name | <and all of the rest>
2       | user2     | ...
3       | user3     | ...

So that, the field role_id I mentioned above is just reference to select the user.

Answer 1

This is one solution. Essentially, you are looking at each user's latest role, and only include it in the output, if the role is 2.

SELECT 
    ur.user_id, ur.role_id 
FROM 
    user_roles ur
WHERE 
    ur.created_at = (SELECT MAX(created_at) 
                     FROM user_roles
                     WHERE user_id = ur.user_id)
    AND ur.role_id = 2
GROUP BY 
    ur.user_id, ur.role_id;

EDIT

Based on the additional information from the comments, the following will return all information from the Users table:

SELECT 
    u.* 
FROM
    users u INNER JOIN (
        SELECT 
            ur.user_id
        FROM 
            user_roles ur
        WHERE 
            ur.created_at = (SELECT MAX(created_at) 
                             FROM user_roles
                             WHERE user_id = ur.user_id)
            AND ur.role_id = 2
        GROUP BY 
            ur.user_id, ur.role_id) tmp ON tmp.user_id = u.user_id;