yii leftjoin 子查询 [ 2.0 版本 ]

SELECT
	A.*, SUM(B.amount)
FROM
	erp_customer A

LEFT JOIN (
	SELECT
		*
	FROM
		erp_order
	WHERE
		`status` = 1
) B ON A.id = B.customer_id
WHERE
	A.`status` = 1
GROUP BY
	A.id

        $query = Customer::find()->alias("A")->where(['A.status'=>Customer::STATUS_ACTIVE]);
        $query->leftJoin('','A.id = B.customer_id','select * from erp_order as B');
        $query->select(['A.*,sum(B.amount) as amount']);
上面的sql语句 用这种形式怎么写 求解