Sum a subquery and group by customer info - sql

Question

I have three tables something like the following:
Customer (CustomerID, AddressState)
Account (AccountID, CustomerID, OpenedDate)
Payment (AccountID, Amount)
The Payment table can contain multiple payments for an Account and a Customer can have multiple accounts.
What I would like to do is retrieve the total amount of all payments on a State by State and Month by Month basis. E.g.
Opened Date| State | Total
--------------------------
2009-01-01 | CA | 2,500
2009-01-01 | GA | 1,000
2009-01-01 | NY | 500
2009-02-01 | CA | 1,500
2009-02-01 | NY | 2,000
In other words, I'm trying to find out what States paid the most for each month. I'm only interested in the month of the OpenedDate but I get it as a date for processing afterwards. I was trying to retrieve all the data I needed in a single query.
I've been trying something along the lines of:
select
dateadd (month, datediff(month, 0, a.OpenedDate), 0) as 'Date',
c.AddressState as 'State',
(
select sum(x.Amount)
from (
select p.Amount
from Payment p
where p.AccountID = a.AccountID
) as x
)
from Account a
inner join Customer c on c.CustomerID = a.CustomerID
where ***
group by
dateadd(month, datediff(month, 0, a.OpenedDate), 0),
c.AddressState
The where clause includes some general stuff on the Account table. The query won't work because the a.AccountID is not included in the aggregate function.
Am I approaching this the right way? How can I retrieve the data I require in order to calculate which States' customers pay the most?

Answer 1

If you want the data grouped by month, you need to group by month:
SELECT AddressState, DATEPART(mm, OpenedDate), SUM(Amount)
FROM Customer c
INNER JOIN Account a ON a.CustomerID = c.CustomerID
INNER JOIN Payments p ON p.AccountID = a.AccountID
GROUP BY AddressState, DATEPART(mm, OpenedDate)
This shows you the monthnumber (1-12) and the total amount per state. Note that this example doesn't include years: all amounts of month 1 are summed regardless of year. Add a datepart(yy, OpenedDate) if you like.

Answer 2

In other words, I'm trying to find out what States paid the most for each month
This one will select the most profitable state for each month:
SELECT *
FROM (
SELECT yr, mon, AddressState, amt, ROW_NUMBER() OVER (PARTITION BY yr, mon, addressstate ORDER BY amt DESC) AS rn
FROM (
SELECT YEAR(OpenedDate) AS yr, MONTH(OpenedDate) AS mon, AddressState, SUM(Amount) AS amt
FROM Customer c
JOIN Account a
ON a.CustomerID = c.CustomerID
JOIN Payments p
ON p.AccountID = a.AccountID
GROUP BY
YEAR(OpenedDate), MONTH(OpenedDate), AddressState
)
) q
WHERE rn = 1
Replace the last condition with ORDER BY yr, mon, amt DESC to get the list of all states like in your resultset:
SELECT *
FROM (
SELECT yr, mon, AddressState, amt, ROW_NUMBER() OVER (PARTITION BY yr, mon, addressstate ORDER BY amt DESC) AS rn
FROM (
SELECT YEAR(OpenedDate) AS yr, MONTH(OpenedDate) AS mon, AddressState, SUM(Amount) AS amt
FROM Customer c
JOIN Account a
ON a.CustomerID = c.CustomerID
JOIN Payments p
ON p.AccountID = a.AccountID
GROUP BY
YEAR(OpenedDate), MONTH(OpenedDate), AddressState
)
) q
ORDER BY
yr, mon, amt DESC

Answer 3

select
AddressState,
year(OpenedDate) as Yr,
month(OpenedDate) as Mnth,
sum(Payment) as SumPayment
from Customer c
inner join Account a
on c.CustomerID=a.CustomerID
inner join Payment p
on a.AccountID=p.AccountID
group by AddressState, month(OpenedDate)