Question

Im making a codeigniter webapp where users can add each other in a contactslist.

The table looks like this:

`id` int(11) NOT NULL AUTO_INCREMENT,
 `user_1` int(11) NOT NULL,
 `user_2` int(11) NOT NULL,
 `accepted` tinyint(2) NOT NULL,
  PRIMARY KEY (`id`)

The userid for the user that makes the request to add the contact is always stored in user_1 column. The other users userid is stored in user_2. user_2 then has to accept the request and the ‘accepted’ column gets updated to 1.

I want to list all contacts that are accepted (WHERE accepted = 1) in a html table, and the contact requests (accepted = 0) in another.
My question is: How can i make a mysql query that selects all the rows and just get the userid from the contact? Its a problem since they can be in either user_1 or user_2 (Depending on if they requested or accepted).

Should i change the db table in some way to achieve this. Or could i make a query (active rcords preferably) that accomplish this?

Any help is appreciated

Thanks in advance

George

Update:

So the final query looks like this:

SELECT DISTINCT users.id, users.username, contacts.accepted 
FROM users
LEFT JOIN contacts ON users.id = contacts.user_1
WHERE contacts.user_2 = ' . $this->session->userdata('user_id') . '
UNION DISTINCT
SELECT DISTINCT users.id, users.username, contacts.accepted 
FROM users 
LEFT JOIN contacts ON users.id = contacts.user_2
WHERE user_1 = ' . $this->session->userdata('user_id')

And works exactly as i described 🙂

Answer 1

Use a UNION query. See the documentation.

SELECT DISTINCT user_1 userid FROM user WHERE accepted = 1
UNION DISTINCT
SELECT DISTINCT user_2 userid FROM user WHERE accepted = 1

About the join, you’d use something like below for each part of the UNION

SELECT DISTINCT users.userid, users.username, contacts.accepted 
FROM users
LEFT JOIN contacts ON users.userid = contacts.user_1
WHERE contacts.user_2 = ?