Get payment total minus amount received - sql-server

Question

I have two tables.
1.Invoice
invoice_Id invoice_no client_id date total_price
-----------------------------------------------------------------------------
2 INV00001 9 2014-10-15 200.00
7 INV00002 9 2014-10-16 560.00
8 INV00003 9 2014-10-21 100.00
11 INV00004 9 2014-10-27 101.00
2.Invoice_payment
InvPayment_id client_id Invoice_Id receipt_no payment_date amount_received discount
--------------------------------------------------------------------------------------------
6 9 8 REC00002 2014-10-31 5.00 0.00
Now I want to get Total Amount Due by Client by totalling the invoice amounts and subtracting any amounts received.
Expected Result:
client_id Total_price Due_Amount
-----------------------------------------------------------------------------
9 961.00 956.00
NOTES:
There will be zero rows if no payments are taken to date.
There could be multiple rows if more than one payment is taken.
Here is what I have tried:
;WITH cte (clientid, invoiceid, paid, disc)
As
(
Select client_id clientId, invoice_Id invoiceId, sum(amount_received) paid, sum(discount) disc
From tbl_Invoice_Payment
Group by invoice_id, client_id
)
Select I.client_id, invoice_Id, invoice_no, I.due_date
,SUM(I.total_price), Isnull(SUM(paid), 0) Paid, (SUM(Total_price) - Isnull(SUM(paid),0) - Isnull(SUM(disc),0)) Balance
--,I.total_price, Isnull(paid, 0) Paid, (Total_price - Isnull(paid,0) - Isnull(disc,0)) Balance
From tbl_invoice I Left join cte On I.client_id = cte.clientId
And I.invoice_id = cte.invoiceid
left join tbl_client C on C.client_id = I.client_id
group by I.client_id, invoice_Id, invoice_no, due_date, account_type, company_name, total_price, paid, disc
order by company_name
But it's not working as intended.

Answer 1

Instead of using a CTE, you can simply add a subquery to return the result of payments made and subtract that value from the total:
SQL Fiddle Demo
Schema Setup:
CREATE TABLE Invoice
([invoice_Id] int, [invoice_no] varchar(8), [client_id] int,
[date] datetime, [total_price] decimal(5,2));
INSERT INTO Invoice
([invoice_Id], [invoice_no], [client_id], [date], [total_price])
VALUES
(2, 'INV00001', 9, '2014-10-15 00:00:00', 200.00),
(7, 'INV00002', 9, '2014-10-16 00:00:00', 560.00),
(8, 'INV00003', 9, '2014-10-21 00:00:00', 100.00),
(11, 'INV00004', 9, '2014-10-27 00:00:00', 101.00);
CREATE TABLE Invoice_Payment
([InvPayment_id] int, [client_id] int, [Invoice_Id] int, [receipt_no] varchar(8),
[payment_date] datetime, [amount_received] decimal(5,2), [discount] int);
INSERT INTO Invoice_Payment
([InvPayment_id], [client_id], [Invoice_Id], [receipt_no], [payment_date],
[amount_received], [discount])
VALUES
(6, 9, 8, 'REC00002', '2014-10-31 00:00:00', 5.00, 0.00);
Query to generate output::
SELECT i.client_id , SUM(i.total_price) AS Total_price,
SUM(i.total_price) - ( SELECT SUM(ip.amount_received)
FROM dbo.Invoice_Payment ip
WHERE i.client_id = ip.client_id
) AS DueAmount
FROM dbo.Invoice i
WHERE client_id = 9
GROUP BY client_id
Results:
| CLIENT_ID | TOTAL_PRICE | DUEAMOUNT |
|-----------|-------------|-----------|
| 9 | 961 | 956 |

Answer 2

Please select the values you want. The problem is related to grouping.
In the group by clause I.client_id, invoice_Id, invoice_no, due_date, account_type, company_name, total_price, paid, disc this much fields are specified. invoice_Id, invoice_no prevent grouping which you need. Remove both invoice_Id and invoice_no from select and group by and try again.