Pre transaction Rolling balance SQL Server 2008 - sql-server-2008

Question

I have a couple of relatively straight forward tables (examples below).
One has accounts details in:
AccountNo | CurrentBalance* | ReferredBalance
12345 | £1254.25 | 1500.00
Current balance refreshes hourly so is not static
Another one has payments:
Accountno | TranasctionNo | TransDate | Amount |
123456 | 558745489 | 01/01/2015 | £25.99 |
123456 | 558745490 | 01/02/2015 | £25.99 |
123456 | 558745491 | 01/02/2015 | £25.99 |
I’ve been tasked with keep a rolling balance based on payments received including a pre transaction amount.
So for example I need to an output to mirror :
AccountNo | TransactionDate | PreTransactionBalance | Amount | Current Balance|
123456 | 01/01/2015 | 1254.25 | 25.99 | 1228.26|
123456 | 01/02/2015 | 1228.26 | 25.99 | 1202.27|
123456 | 01/03/2015 | 1202.27 | 25.99 | 1176.28|
123456 | 01/03/2015 | 1176.28 | -100 | 1276.28|
I’ve added the negative in as it will need to calculate debits as well as credits.
Can't quiet work out how to get the rolling pre-transaction totals to work. Hopefully this is clear enough!

Answer 1

You can use SUM(amount) OVER() to get rolling amount based on the TransactionNo and then calculate pre transaction and current balance from this value.
Sample Data
DECLARE #Account TABLE
(
AccountNo VARCHAR(10) ,
CurrentBalance MONEY,
ReferredBalance MONEY
)
DECLARE #AccountPayment TABLE
(
Accountno VARCHAR(10),TranasctionNo VARCHAR(10),TransDate DATE,Amount MONEY
)
insert into #Account VALUES
('12345','£1254.25','1500.00');
insert into #AccountPayment values
('12345','558745489','01/01/2015','£25.99'),
('12345','558745490','01/02/2015','£25.99'),
('12345','558745491','01/02/2015','£25.99'),
('12345','558745492','01/02/2015','-100');
Query
SELECT AP.AccountNo,
TransDate,
A.CurrentBalance - SUM(amount) OVER(ORDER BY TranasctionNo) + amount as PreTransactionBalance ,
amount,
A.CurrentBalance - SUM(amount) OVER(ORDER BY TranasctionNo) Current_Balance
FROM #AccountPayment AP
INNER JOIN #Account A
ON AP.Accountno = A.Accountno
Edit
It seems ORDER BY is not supported with in SUM() OVER() in SQL Server 2008 / SQL Server 2008 R2. As per msdn
ORDER BY Clause cannot be used with aggregate window functions.
We can use CROSS APPLY like this.
SELECT AP.AccountNo,
TransDate,
A.CurrentBalance - pre_amount as PreTransactionBalance ,
amount,
A.CurrentBalance - pre_amount - amount Current_Balance
FROM #AccountPayment AP
INNER JOIN #Account A
ON AP.Accountno = A.Accountno
CROSS APPLY
(
select ISNULL(sum(amount),0) as pre_amount
from #AccountPayment ap1
where ap1.Accountno = ap.Accountno and ap1.TranasctionNo < ap.TranasctionNo
) as b
Output
AccountNo TransDate PreTransactionBalance amount Prev_Payments
12345 2015-01-01 1254.25 25.99 1228.26
12345 2015-01-02 1228.26 25.99 1202.27
12345 2015-01-02 1202.27 25.99 1176.28
12345 2015-01-02 1176.28 -100.00 1276.28
SQL Fiddle