with Daily(subscription_date, refund) as
(select d, avg(payment_money) from
	(select S.Id, cast(S.datetime as date) as d, P.payment_money from Subscribtion S
	outer apply
	(select sum(P.money) as payment_money from Payment P
		where P.UserId = S.UserId and P.datetime between S.datetime and dateadd(day, 1, S.datetime) ) P
	) PerSubsription
  group by d)
select D1.subscription_date, avg(D2.refund) refund_past_week from Daily D1
	left join Daily D2 on DateDiff(day, D2.subscription_date, D1.subscription_date) between 0 and 6