declare @potatos table(id bigint, created_date date, shop_id bigint)
declare @potatos_ids table(id bigint)
declare @shop_ids table(id bigint)

insert into @potatos_ids values(1), (2), (3), (4), (5), (6), (7), (8), (9)
insert into @shop_ids values(1), (2), (3), (4), (5), (6), (7), (8), (9)

insert into @potatos
select s.id * 1000 + p.id * 100 + p2.id * 10 + p3.id, DATEADD(month, -p3.id, GETDATE()), p2.id
from @potatos_ids p
cross join @shop_ids s
cross join @potatos_ids p2
cross join @potatos_ids p3

;with groupped_potatos as(
	select o.shop_id, MONTH(o.created_date) as potato_month, COUNT(*) as potatos_count
	from @potatos o
	where o.created_date >= '2012-01-01'
		and o.created_date <= '2012-12-31'
		group by o.shop_id, MONTH(o.created_date)
)

select	
	g.*,
	(
		select SUM(g2.potatos_count) from groupped_potatos g2
		where g2.potato_month >= 1
		and g2.potato_month <= g.potato_month
		and g2.shop_id = g.shop_id
		group by g2.shop_id
	) as accumulated_count
from groupped_potatos g
order by g.potato_month