SQL failing to add value from previous row into the next - sql

Question

I am trying to add the value of the previous row to the current row into the column cumulative
Select
Ddate as Date, etype, Reference, linkacc as ContraAcc,
Description,
sum(case when amount > 0 then amount else 0 end) as Debits,
sum(case when amount < 0 then amount else 0 end) as Credits,
sum(amount) as Cumulative
from
dbo.vw_LT
where
accnumber ='8400000'
and [DDate] between '2016-04-01 00:00:00' and '2016-04-30 00:00:00'
and [DataSource] = 'PAS11CEDCRE17'
group by
Ddate, etype, Reference, linkacc, Description, Amount
Output(what i am getting):
Date Reference ContraAcc Description Debits Credits Cumulative
--------------------------------------------------------------------------
2016-04-01 CC007 8000000 D/CC007 0 -39.19 -39.19
2016-04-01 CC007 8000000 D/CC007 1117.09 0 1117.09
2016-04-01 CC009 8000000 CC009 2600 0 2600
in the cumulative column should like below(what i need):
Date Reference ContraAcc Description Debits Credits Cumulative
--------------------------------------------------------------------------
2016-04-01 CC007 8000000 D/CC007 0 -39.19 -39.19
2016-04-01 CC007 8000000 D/CC007 1117.09 0 1077.9
2016-04-01 CC009 8000000 CC009 2600 0 3677.9

Answer 1

Before we delve into the solution, let me tell you that if you are using SQL Server version more than 2012, there are LAG and LEAD, which can help you to solve this.
I am not giving you an exact query to solve your problem (as we dont know what your primary key for that table is), but you can get the idea by seeing the below example
DECLARE #t TABLE
(
accountNumber VARCHAR(50)
,dt DATETIME
,TransactedAmt BIGINT
)
INSERT INTO #t VALUES ('0001','7/20/2016',1000)
INSERT INTO #t VALUES ('0001','7/21/2016',-1000)
INSERT INTO #t VALUES ('0001','7/22/2016',2000)
INSERT INTO #t VALUES ('0002','7/20/2016',500)
INSERT INTO #t VALUES ('0002','7/21/2016',-500)
INSERT INTO #t VALUES ('0002','7/22/2016',2000)
;WITH CTE AS
(
SELECT ROW_NUMBER() OVER(Partition by accountNumber order by dt) as RN, *
FROM #t
),CTE1 AS
(
SELECT *,TransactedAmt As TotalBalance
FROM CTE WHERE rn = 1
UNION
SELECT T1.*,T1.TransactedAmt + T0.TransactedAmt as TotalBalance
FROM CTE T1
JOIN CTE T0
ON T1.accountNumber = T0.accountNumber
AND T1.RN = T0.RN+1
AND T1.RN > 1
)
select * from CTE1 order by AccountNumber