How to run subqueries in cakephp - php

Question

Cakephp 2.6
I have a Model, Temps, which has many tickets. In the index view of Temps I want to return for each record, the ticket with the date closest to the current date.
In mySQL it can be done as
'SELECT expiry_date FROM uploads WHERE expiry_date > CURDATE() ORDER BY expiry_date ASC LIMIT 1'
But I don't know how to run this as a sub query. My Current query to generate my results is as follows: (bearing in mind this has been configured for datatables) Tickets is an alias for the Upload Model
public function getAjaxIndexData($data) {
$tokens = explode(" ", $data['searchString']);
$conditions = array(
$this->alias . '.deleted' => false,
'OR' => array(
'CONCAT(' . $this->alias . '.first_name," ",' . $this->alias . '.last_name) LIKE' => '%' . implode(' ', $tokens) . '%',
),
$data['columnsFilter']
);
$fields = array(
'id',
'full_name',
'pps_number',
'mobile',
'email',
'start_date',
'time_served'
);
$order = array(
$data['orderField'] => $data['order']
);
$contain = array(
'LocalOffice.name',
);
$options = array(
'conditions' => $conditions,
'fields' => $fields,
'order' => $order,
'contain' => $contain,
'limit' => $data['limit'],
'offset' => $data['start']
);
$optionsNoFields = array(
'conditions' => $conditions,
'contain' => $contain,
);
$result['draw'] = $data['draw'];
$result['recordsTotal'] = $recordTotal = $this->find('count');
$result['recordsFiltered'] = $this->find('count', $optionsNoFields);
$result['data'] = $this->find('all', $options); //standard search
$result['data'] = $this->formatTable($result['data']);
return json_encode($result);
}
Within this query I would like to add a field that shows the nearest expiry date for each Temp.
How would I construct this?

Answer 1

Dynamically create a virtual field:
$this->virtualFields['nearest'] = '(SELECT expiry_date FROM uploads WHERE expiry_date > CURDATE() AND uploads.owner_id = '.$this->alias.'.ticket_id ORDER BY expiry_date ASC LIMIT 1')';
Then adjust your fields array
$fields = array(
'id',
'full_name',
'pps_number',
'mobile',
'email',
'start_date',
'time_served',
'nearest'
);
Also, the query could be rewritten as ("temp" needs to be replaced with the model alias)
SELECT MIN(expiry_date)
FROM uploads
WHERE expiry_date > CURDATE()
AND uploads.owner_id = temp.ticket_id;
Which means that a potentially better performing query would be to move that subquery out of the columns of the SELECT statement to a JOIN. For example:
SELECT *
FROM temp
LEFT JOIN (SELECT MIN(expiry_date) AS expiry,owner_id
FROM uploads
WHERE expiry_date > CURDATE())
GROUP BY owner_id) AS next_dates
ON next_dates.owner_id = temp.ticket_id;