Accessing associated models of HABTM relationships via bindModel() w/o recursion

Question 1

As I understand it, this is the problem; A user has a list of available modules through their courses. We want to find available modules that the user has not completed. In other words, we have to find a user's course's modules which are not in that user's modules.

Here's the best way I can think of doing that:

$modules = $this->User->Module->find('all', array(
    'joins' => array(
        array(
            'table' => 'courses_modules',
            'alias' => 'CoursesModule',
            'type' => 'LEFT',
            'conditions' => array('CoursesModule.module_id = Module.id'),
        ),
        array(
            'table' => 'courses_users',
            'alias' => 'CoursesUser',
            'type' => 'LEFT',
            'conditions' => array('CoursesUser.course_id = CoursesModule.course_id'),
        ),
        array(
            'table' => 'modules_users',
            'alias' => 'ModulesUser',
            'type' => 'LEFT',
            'conditions' => array(
                'ModulesUser.module_id = Module.id',
                'ModulesUser.user_id' => $userId,
            ),
        ),
    ),
    'conditions' => array(
        'CoursesUser.user_id' => $userId,
        'ModulesUser.id' => null,
    ),
    'recursive' => -1,
));

Which should build a query like this:

SELECT Module.* FROM modules AS Module
LEFT JOIN courses_modules AS CoursesModule
    ON (CoursesModule.module_id = Module.id)
LEFT JOIN courses_users AS CoursesUser
    ON (CoursesUser.course_id = CoursesModule.course_id)
LEFT JOIN modules_users AS ModulesUser
    ON (ModulesUser.module_id = Module.id
        AND ModulesUser.user_id = $userId)
WHERE CoursesUser.user_id = $userId
AND ModulesUser.id IS NULL

The first two joins along with the user_id condition will get all the available modules. Rather than getting the user, their courses and then that course's modules we work backwards (kind of); we get the modules and join the courses to which we join the users. Once we add the user_id condition the association will be filtered and only modules that can be joined to the user will be found. Since we are starting with the modules there won't be any duplicates, we don't know (or care) which course was used to make the link.

With those available modules we then join the modules a user has completed and limit the records to those that couldn't be joined.

The CakePHP documentation has more info on joining tables.

Edit :

If you want to set the course IDs manually, you can do this:

$modules = $this->User->Module->find('all', array(
    'joins' => array(
        array(
            'table' => 'courses_modules',
            'alias' => 'CoursesModule',
            'type' => 'LEFT',
            'conditions' => array('CoursesModule.module_id = Module.id'),
        ),
        array(
            'table' => 'modules_users',
            'alias' => 'ModulesUser',
            'type' => 'LEFT',
            'conditions' => array(
                'ModulesUser.module_id = Module.id',
                'ModulesUser.user_id' => $userId,
            ),
        ),
    ),
    'conditions' => array(
        'CoursesModule.course_id' => $courseIds,
        'ModulesUser.id' => null,
    ),
    'recursive' => -1,
));

Question 2

There's something wrong with the way you set up your relationships. Could you post to show what you've done to set up the relationships, plus what the SQL query is that's giving the error? I'm also confused about what exactly your query is supposed to do.

I can make a few observations already though:

Course does not seem to be defined in your query, which is why you're getting a sql error. Probably there is something wrong with your relationships regarding Course.
If you're trying to do a HABTM relationship between Users and Modules and Courses and Modules, why are you doing creating a hasOne relationship between Module and CoursesModules and Module and UsersModules?

The short version of what I'm wondering is, shouldn't that be a hasMany instead of a hasOne?

The long version is, occasionally, when you have a join table like that, you'll need to for some reason create a relationship with the join table itself rather than just using HABTM (where when you get the data, the data in the join table is not included). Generally this is because there is data besides the two foreign keys that must also be stored in the join table. But in that case, you should be using what is known as a has many through relationship. If it's not necessary to use a has many through, you should just be using HABTM with users and courses, and not be creating relationships with directly with the join tables at all. http://book.cakephp.org/2.0/en/models/associations-linking-models-together.html#hasmany-through-the-join-model

Conditions for related models need to be in the contain options. Keep in mind that the normal behavior of Cake is to get related model data in additional queries, rather than doing a join and getting it all in one query. http://book.cakephp.org/2.0/en/core-libraries/behaviors/containable.html

Accessing associated models of HABTM relationships via bindModel() w/o recursion

The Problem In A Nutshell

Concrete Example / Actual Circumstances

UPDATE

Model Associations

Edit :