How to sum transaction amounts for different time intervals in sql server?

Let say I have table called Transactions and have 3 following columns:

Customerid
TranscationDate
TransactionAmount

So I need to sum transaction amounts for each customer in different date intervals. For example, transaction amount for last 10 days, transaction amount from last 10 days to last 30 days and etc..

this is what I have tried. It work, but running time is ultimately slow.

select customerid
,SUM ( case when transactiondate > @date1 and TOPUPDATE <@date0 then transactionamount else 0 end) AS Amount_last10
,SUM ( case when transactiondate > @date2 and TOPUPDATE <@date1 then transactionamount else 0 end) AS Amountlast10_to_last20


,SUM ( case when transactiondate > @date1 and TOPUPDATE <@date0 then transactionamount else 0 end) AS count_last10
,SUM ( case when transactiondate > @date2 and TOPUPDATE <@date1 then transactionamount else 0 end) AS count_last10_to_20

from TransactionData t
group by customerid 

For better understanding I write down what I need

Customer_id  Amount_last10   Amountlast10_to_last20    count_last10    count_last10_to_20
11234        100             200                          3             1 

Please consider that I have many many rows, so I need make my query running time as less as possible.

Answer

If I understand correctly, you want conditional aggregation:

select Customerid, sum(TransactionAmount) as amount_total,
       sum(case when datediff(day, TransactionDate, getdate()) between 0 and 9
                then TransactionAmount else 0
           end) as total_0_9,
       sum(case when datediff(day, TransactionDate, getdate()) between 10 and 19
                then TransactionAmount else 0
           end) as total_10_19,
       . . .
from Transactions t
group by Customerid;

For performance, you should add a where clause so you only aggregate the data you need. For instance, for the above two columns:

where TransactionDate >= dateadd(day, -19, convert(date, getdate())