Yii2 using ActiveQuery that uses sub-query on same Model - mysql

Question

I have a Comments table that have parent_id foreign key that points to itself to enable threaded comment.
Comments
id INT UNSIGNED NOT NULL
parent_id INT UNSIGNED NULL
comment TEXT NOT NULL
created_time DATETIME NOT NULL
The original ActiveQuery is like this
class CommentActiveQuery extends \yii\db\ActiveQuery {
public function andWhereIsNotRemoved() {
return $this->andWhere(['isRemoved' => Comment::STATUS_IS_NOT_REMOVED]);
}
public function andWhereParentIdIs($parentId) {
return $this->andWhere(['parentId' => $parentId]);
}
public function orderByNewestCreatedTime() {
return $this->orderBy(['createdTime' => SORT_DESC]);
}
}
Now I want to sort the comments by the newest active reply.
The query is basically like this
SELECT `*`, `last_reply_time`
FROM `Comments`
WHERE `parent_id` IS NULL
ORDER BY `last_reply_time` DESC;
I'm thinking the last_reply_time is a subquery
SELECT MAX(created_time)
FROM `Comments`
WHERE `parent_id` = :something
How to build this using the CommentActiveQuery above. The farthest I can get is like this
public function orderByNewestActiveChildCreatedTime() {
return $this->addSelect([
'last_reply_time' => $subQuery
])->orderBy(['last_reply_time' => SORT_DESC]);
}
With what should I replace the $subQuery variable above? Or is there a better way?

Answer 1

$subQuery = new \yii\db\Query();
$subQuery->select(["max(subQ.created_time)"]);
$subQuery-> from('comments subQ');
$subQuery->where([
'parent_id' => $parentId
]);
$query = new \yii\db\Query();
$query->select([
'C.*',
$subQuery
]);
$query->from('Comments C');
$query->andWhere(
'parent_id is Null'
);
$command = $query->createCommand();
/*
Printing the command will result following sql with $parentId = 1
SELECT
`C`.*, (
SELECT
max(subQ.created_time)
FROM
`comments` `subQ`
WHERE
`parent_id` =: qp0
) AS `1`
FROM
`Comments` `C`
WHERE
parent_id IS NULL
*/
print_r($command->sql);
I am not sure about ORDER BY last_reply_time DESC; Assuming last_reply_time is db table attribute and is different from the subquery. You can simply add orderBy in the query by doing $query->orderBy('last_reply_time DESC')
I hope this would be helpful to you.Cheers :)