还是执行自己写的sql方便，如下是执行自定义的sql的例子，你参看看看

$sql = "SELECT SUM(commentNum) AS num FROM db_article_list WHERE `type`='isOpen'";
$commentNum = Yii::$app->db->createCommand($sql)->queryOne();

改一下select就可以了

$model->find()->select(['num'=>'SUM(commentNum)'])->where(['type'=>'isOpen'])->one();

当然有sum方法！

1. Query

(new Query())->from('table')->sum('field');

1. AR

Article::find()->sum('field');

$countQuantity = OrderWsyReturnGoods::find()->where(['order_id' => $returnGoods->order_id, 'goods_sn' => $returnGoods->goods_sn,'status' => OrderWsyReturnGoods::STATUS_DONE])->sum('return_quantity');

之前的一段代码，看着改变量就行了，我写了三个筛选条件。