Recursive SQL- How can I get this table with a running total? - sql

Question

ID debit credit sum_debit
---------------------------------
1 150 0 150
2 100 0 250
3 0 50 200
4 0 100 100
5 50 0 150
I have this table, my problem is how to get sum_debit column which is the total of the previous row sum_debit with debit minus credit (sum_debit = sum_debit + debit - credit).
each new row I enter debit but credit data is zero, or by entering the value of credit and debit is zero. How do I get sum_debit?

Answer 1

In SQL-Server 2012, you can use the newly added ROWS or RANGE clause:
SELECT
ID, debit, credit,
sum_debit =
SUM(debit - credit)
OVER (ORDER BY ID
ROWS BETWEEN UNBOUNDED PRECEDING
AND CURRENT ROW
)
FROM
CreditData
ORDER BY
ID ;
Tested in SQL-Fiddle
We could just use OVER(ORDER BY ID) there and the result would be the same. But then the default would be used, which is RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW and there are efficiency differences (ROWS should be preferred with running totals.)
There is a great article by #Aaron Bertrand, that has a thorough test of various methods to calculate a running total: Best approaches for running totals – updated for SQL Server 2012
For previous versions of SQL-Server, you'll have to use some other method, like a self-join, a recursive CTE or a cursor. Here is a cursor solution, blindly copied from Aaron's blog, with tables and columns adjusted to your problem:
DECLARE #cd TABLE
( [ID] int PRIMARY KEY,
[debit] int,
[credit] int,
[sum_debit] int
);
DECLARE
#ID INT,
#debit INT,
#credit INT,
#RunningTotal INT = 0 ;
DECLARE c CURSOR
LOCAL STATIC FORWARD_ONLY READ_ONLY
FOR
SELECT ID, debit, credit
FROM CreditData
ORDER BY ID ;
OPEN c ;
FETCH NEXT FROM c INTO #ID, #debit, #credit ;
WHILE ##FETCH_STATUS = 0
BEGIN
SET #RunningTotal = #RunningTotal + (#debit - #credit) ;
INSERT #cd (ID, debit, credit, sum_debit )
SELECT #ID, #debit, #credit, #RunningTotal ;
FETCH NEXT FROM c INTO #ID, #debit, #credit ;
END
CLOSE c;
DEALLOCATE c;
SELECT ID, debit, credit, sum_debit
FROM #cd
ORDER BY ID ;
Tested in SQL-Fiddle-cursor

Answer 2

Assuming "have" is your data table, this should be an ANSI SQL solution:
select h.*, sum(i.debit) as debsum, sum(i.credit) as credsum, sum(i.debit) - sum(i.credit) as rolling_sum
from have h inner join have i
on h.id >= i.id
group by h.id, h.debit, h.credit
order by h.id
In general, the solution is to join the row to all rows preceding the row, and extract the sum of those rows, then group by everything to get back to one row per what you expect. Like this question for example.