Question

I have three columns I need to join which comes from 3 different tables,

Contributions table:

+-----------+---------------------+
| record_id | contributor_user_id |
+-----------+---------------------+
|         1 |                   2 |
+-----------+---------------------+
|         1 |                   5 |
+-----------+---------------------+

Members table:

+--------------+---------+
| username     | user_id |
+--------------+---------+
| Test         |       1 |
+--------------+---------+
| Test2        |       5 |
+--------------+---------+
| Test3        |       6 |
+--------------+---------+

Records table:

+---------+-----------+
| user_id | record_id |
+---------+-----------+
|      28 |         1 |
+---------+-----------+

For what I need to return is the username and user_id for displaying the record owner. Also, display the username and the user_id, but this can be multiple (more than 1+ user). I’ve tried this:

SELECT usr.username,
       usr.user_id,
       rec.record_id,
       contrib.record_id,
       contrib.contributor_user_id
FROM 
(
    records rec

    INNER JOIN members usr ON rec.user_id = usr.user_id

    # this returns records as NULL
    LEFT OUTER JOIN contributions contrib ON rec.record_id = contrib.record_id AND contrib.contributor_user_id = usr.user_id

    # this works, but I need the username to be displayed too
    LEFT OUTER JOIN contributions contrib ON rec.record_id = contrib.record_id
)
WHERE rec.record_id = 1

Answer 1

Try nesting the join for contributing users inside of the left join to contributions.

SELECT u.username, u.user_id, r.record_id, u2.username as ContributorName, u2.user_id as ContributorId
    FROM records r
        INNER JOIN members u
            ON r.user_id = u.user_id
        LEFT JOIN contributions c
            INNER JOIN members u2
                ON c.contributor_user_id = u2.user_id
            ON r.record_id = c.record_id
    WHERE r.record_id = 1