create table Sale
(
 customerID int
,OrderID int
,date_ datetime
)

insert into Sale
		  select '123','5465363','2012/10/01'
union all select '123','5465363','2012/10/01'
union all select '124','6545344','2012/10/01'
union all select '124','6545348','2012/10/02'
union all select '124','6545353','2012/10/04'



select 
	 s1.customerID
	,s1.OrderID
	,s1.date_
	,row_number() over (partition by s1.CustomerID order by (select getdate())) as showOrder
	,showOrder2 =  (
					select count(CustomerID)
						from
							sale as s2							
					where
						s2.CustomerID = s1.CustomerID
					and s2.Date_ <= s1.Date_ 
					)
from sale as s1

Declare @T table
(
 customerID int
,OrderID int
,date_ datetime
)

insert into @T
		  select '123','5465363','2012/10/01'
union all select '123','5465363','2012/10/01'
union all select '124','6545344','2012/10/01'
union all select '124','6545348','2012/10/02'
union all select '124','6545353','2012/10/04'


Select identity(int,1,1)ID,* into #ROWNUMBER
from @T

select 
	 s1.customerID
	,s1.OrderID
	,s1.date_
	,row_number() over (partition by s1.CustomerID order by (select getdate())) as showOrder
	,showOrder2 =  (
					select count(*)
						from
							#ROWNUMBER as s2							
					where
						s2.CustomerID = s1.CustomerID
					and ID < = s1.ID
					)
from #ROWNUMBER as s1