如何在yii2中构建一个Query对象？

And how could I use that object with activedataprovider for gridview widget in yii2?

SELECT `activated_promo`.*
    ,rides_promo_count_view.count
FROM `activated_promo`
LEFT JOIN `promo_code` `promo` ON `activated_promo`.`promo_id` = `promo`.`id`
LEFT JOIN `users` `customer` ON `activated_promo`.`userID` = `customer`.`ID`
LEFT JOIN rides_promo_count_view ON promo.id = rides_promo_count_view.promo_id

Assuming you have ActiveRecord class for each mysql table, you can use the below query.

    //By Assuming you have Active Record for each table
    $activedPromo = ActivitedPromo::find()
        ->select('activated_promo.*','rides_promo_count_view.count')
        ->leftJoin('`promo_code` `promo`', '`activated_promo`.`promo_id` = `promo`.`id`')
        ->leftJoin('`users` `customer`', '`activated_promo`.`userID` = `customer`.`ID`')
        ->leftJoin('rides_promo_count_view', 'promo.id = rides_promo_count_view.promo_id')
        ->all();

the above way is one of it and for alternatives(for example use joinWith), you can take a look at the document in YII ActiveRecord