Question

The following query returns an array containing the proper ids, but null for all values.

If I remove the aggregation function (AVG()), it returns values (not the averaged ones of course), if I choose e.g. find('all') it returns the average, but not in the list format I want (I could work with that, but I want to try to do it with 'list' first).

$progress = $this->Trial->find('list', array(
    'fields' => array(
        'Trial.session_id',
        'AVG(Trial.first_reaction_time_since_probe_shown) AS average_reaction_time'
    ),
    'group' => 'Trial.session_id',
    'conditions' => array(
        'Trial.first_valid_response = Trial.probe_on_top',
        'TrainingSession.user_id IS NOT NULL'
    ),
    'contain' => array(
        'TrainingSession' => array(
            'conditions' => array(
                'TrainingSession.user_id' => $this->Auth->user('id') 
            )
        )
    ),
    'recursive' => 1,
));

The generated SQL query returns exactly the result I want, when I send it to the DB via PhpMyAdmin.

SELECT 
    `Trial`.`session_id`, 
    AVG(`Trial`.`first_reaction_time_since_probe_shown`) AS average_reaction_time 
FROM 
    `zwang`.`trials` AS `Trial` 
LEFT JOIN 
    `zwang`.`training_sessions` AS `TrainingSession` ON (
        `Trial`.`session_id` = `TrainingSession`.`id` AND
        `TrainingSession`.`user_id` = 1
    )
WHERE 
    `Trial`.`first_valid_response` = `Trial`.`probe_on_top` 
GROUP BY 
    `Trial`.`session_id`

I’ve examined the source for find(‘list’). I think it’s due to the “array path” for accessing the list getting screwed up when using functions in the query, but I couldn’t fix it yet (or recognise my abuse of CakePHP logic).

Answer 1

Once I posted the question, Stackoverflow started relating the correct answers to me.

Apparently, it can’t be done with 'list' without virtualFields.
I didn’t expect that because it worked using the other find-types.

$this->Trial->virtualFields = array(
    'average_reaction_time' => 'AVG(Trial.first_reaction_time_since_probe_shown)'
);
$progress = $this->Trial->find('list', array(
    'fields' => array('Trial.session_id','average_reaction_time')
    /* etc... */ 
));