How to use subquery in the join function of Yii framework 2 ActiveRecord? - sql

Question

Below is my pure SQL query.
SELECT a.*, b.*
FROM a
INNER JOIN b
ON a.id = b.a_id
INNER JOIN (
SELECT a_id, MAX(add_time) AS max_add_time
FROM b
GROUP BY a_id
) m
ON b.a_id = m.a_id AND b.add_time = m.max_add_time
ORDER BY b.add_time DESC
I have the subquery in the second INNER JOIN. Below my active query.
$subQuery = B::find()->select(['a_id', 'MAX(add_time) AS max_add_time'])->groupBy('a_id');
$query = A::find()->innerJoin('b', 'a.id = b.a_id')
->innerJoin('(' .
$subQuery->prepare(Yii::$app->db->queryBuilder)
->createCommand()
->rawSql
. ') m', 'b.a_id = m.a_id AND a.add_time = m.max_add_time ')
->orderBy('b.add_time DESC');
It works fine, but I do not like the way I use the subquery in the second INNER JOIN. What I want to approach with this query is to select the left table inner join with right table, group by a_id and order by the add_time (DESC) of the right table. How should I better use the subquery in the second INNER JOIN?

Answer 1

The snippet below is untested but it should be something like that. If you read the docs (at http://www.yiiframework.com/doc-2.0/yii-db-query.html#innerJoin()-detail) you can see an array with a subquery is also valid input, with the key being the alias.
$subQuery = B::find()
->select(['a_id', 'MAX(add_time) AS max_add_time'])
->groupBy('a_id');
$query = A::find()
->innerJoin('b', 'a.id = b.a_id')
->innerJoin(['m' => $subQuery], 'b.a_id = m.a_id AND a.add_time = m.max_add_time')
->orderBy('b.add_time DESC');

Answer 2

Having created the join, if you need to use any of the columns returned by the subQuery, you need to add properties to the Yii2 model class, e.g.
$subQuery = FinancialTransaction::find()
->select( new \yii\db\Expression( 'SUM(amount) as owing') )
->addSelect('booking_id')
->groupBy('booking_id');
$query = $query
->addSelect(['b.*', 'owing'])
->leftJoin(['ft' => $subQuery], 'b.booking_display_id = ft.booking_id');
To access "owing" the model has to have the property (PHPdoc optional):
/**
* #var float
*/
public $owing=0;