Displaying MySQL data into HTML table (clearly explained)

Question

Ok, I have an app as described in this post: http://stackoverflow.com/questions/1623105/good-database-structure-for-a-new-web-app

I've prepared a scenario to make my question as clear as possible:

Users table:
    +----------+-----------------+
    | user_id  | email           |
    +----------+-----------------+
    | user_1   | [email protected] |
    | user_2   | [email protected] |
    | user_3   | [email protected] |
    | user_4   | [email protected] |
    +----------+-----------------+

*Notice user_3 and user_4 do not have their own domains

Domains table:
    +-----------+------------+
    | owner_id  | domain     |
    +-----------+------------+
    | user_1    | dom-1.com  | 
    | user_1    | dom-2.com  |
    | user_2    | dom-3.com  |
    +------------------------+

The table below, shows who is a user of a domain and who the owner is:

User-Domain table:
    +----------+-------------+-----------+
    | user_id  | domain      | owner_id  |
    +------------------------+-----------+
    | user_1   | dom-1.com   | user_1    |
    | user_1   | dom-2.com   | user_1    |
    | user_2   | dom-3.com   | user_2    |
    | user_3   | dom-1.com   | user_1    |
    | user_3   | dom-2.com   | user_1    |
    | user_4   | dom-1.com   | user_1    |
    +------------------------+-----------+

My question is, how do I output a list of each user who is using a given user's domain, in the following format?

For example (the following is an HTML table):

List of users who are using User_1's domains (HTML TABLE):
        +-------------------+-----------------------+
        | Email             | domains               |
        +-------------------+-----------------------+
        | [email protected]   | dom-1.com, dom-2.com  |
        | [email protected]   | dom-1.com             |
        +-------------------+-----------------------+

Answer 1

This query should give you the results. Displaying a HTML table from it should be easy enough.

SELECT
   u.email,
   group_concat(d.domain SEPARATOR ', ')
FROM
   domains d
   JOIN user_domain ud ON d.domain=ud.domain AND d.owner_id=ud.owner_id AND d.owner_id!=ud.user_id
   JOIN users u on ud.user_id=u.user_id
WHERE d.owner_id='user_1'
GROUP BY u.email

You basically select all domains owned by 'user_1', then all user_ids for these domains, and then all users for these user_ids. After that, you group the results by the user's email and concatenate all domain names the user is using.