Question

I have following two tables ‘USERS’ and ‘GROUPS’:

USERS 
-id
-name
-groupid

GROUP 
-id
-name

I’d like to return all users along with their group’s name and group id. It should be an outer join on group id field correct?

Answer 1

You can use a LEFT JOIN between users and groups so that users who are not in a group still show up in the result set, but with group name and id NULL:

SELECT 
    a.*,
    b.name AS group_name
FROM
    users a
LEFT JOIN
    `group` b ON a.group_id = b.id

Side note: Ensure that you’re encasing the table name group in backticks because it is a reserved keyword.

The result-set should look something like:

id       |       name       |       group_id       |       group_name
-----------------------------------------------------------------------------
1        |       John       |       5              |       ThisIsGroup5
3        |       Tim        |       3              |       ThisIsGroup3
6        |       NotInGroup |       NULL           |       NULL

Changing LEFT to INNER in the above query would INNER JOIN the two tables and exclude the user “NotInGroup” from the result-set.