Assign second role to user

If you first fetch a WP_User object with get_userdata(), you should then be able to add your additional role with the add_role() method, like so:

$user = get_userdata($user_id);
$user->add_role('partner');

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)