SQL deduct some numbers from rows conditionally - tsql

Question

I have a table (showing temp table)
CREATE TABLE #TempTable
(
TempID INT IDENTITY(1,1) NOT NULL PRIMARY KEY,
CustID INT NOT NULL,
RODate DATE NULL,
Operation INT NULL
);
This table has this sample data:
INSERT INTO #TempTable (CustID, RODate, Operation)
VALUES (10, DATEADD(MONT, -2, GETDATE()), 2),
(10, DATEADD(MONT, -1, GETDATE()), 3),
(10, GETDATE(), 5)
So table have below data
TempID CustID RODate Operation
-----------------------------------------------------------
1 10 2019-03-17 2
2 10 2019-04-17 3
3 10 2019-05-17 5
Requirement is I will get one integer variable in parameter which is #noOfOperation, let's say its value is 10
I will also get no of months in parameter, let's say it's 3
I have to query the table to return data for last 3 months only (excluding current month (date asc)
Then I have to deduct #noOfOperation from the table and update.
Deduction will be based on availability in operation column.
For example: in this case first we will deduct from 2019-03-17
10 - 2 = 8 (operation column for this row becomes 0)
Next we will deduct from 2019-04-17
8 - 3 = 5 (operation column for this row becomes 0)
Similarly for 2019-05-17
5-5 = 0 (operation column for this row becomes 0)
I have to check if #noOfOperation is less than or more than the number of operation of individual months then do the above accordingly

Answer 1

Check this out, The idea is to use the accumulated operation and then subtracted the needed value as below:
declare #TempTable TABLE
(
TempID INT IDENTITY(1,1) NOT NULL PRIMARY KEY,
CustID INT NOT NULL,
RODate DATE NULL,
Operation INT NULL
);
INSERT INTO #TempTable (CustID, RODate, Operation)
VALUES (10, DATEADD(MONTH, -2, GETDATE()), 5),
(10, DATEADD(MONTH, -1, GETDATE()), 6),
(10, GETDATE(), 7)
select * from #TempTable
Declare #noOfOperation int =8
Declare #noOfMonths int =3
Declare #StartDate date,#DateEnd date,#avNoOfOperation int
--get the range you are working for
select
#StartDate=cast(cast(year(dateadd(Month,-#noOfMonths+1,getdate())) as varchar(4))+'-'+cast(Month(dateadd(Month,-#noOfMonths+1,getdate())) as varchar(2))+'-01' as date)
,#DateEnd=dateadd(day,-1,cast(cast(year(getdate()) as varchar(4))+'-'+cast(Month(getdate()) as varchar(2))+'-01' as date)) ;
--get the total of avaliable operation, for validating before subtracting
select #avNoOfOperation=sum(t.Operation) from #TempTable t where cast(t.RODate as date) between #StartDate and #DateEnd
--review the variables if needed
--select #StartDate [#StartDate],#DateEnd [#DateEnd],#avNoOfOperation [#avNoOfOperation]
if(#avNoOfOperation>=#noOfOperation and #noOfOperation>0)
begin
--only here we can start subtracting
;with DataIncluded as (
select *,#noOfOperation [noOfOperation],sum(Operation) over (order by RODate) [AcOp] from #TempTable t where cast(t.RODate as date) between #StartDate and #DateEnd
),SubtractDataSet as (
select *,AcOp-#noOfOperation [leftOp],
case when (AcOp-#noOfOperation)<=0 then 0 else
case when (AcOp-#noOfOperation)<Operation then AcOp-#noOfOperation else Operation end end [UpOp]
from DataIncluded
)
Update #TempTable
set A.Operation=B.[UpOp]
From #TempTable A
inner join SubtractDataSet B on A.TempID=B.TempID
end
select * from #TempTable
Note: Im not using the current month so my output is different then the one you suggested. if the inputs was as follow:
TempID CustID RODate Operation
1 10 2019-03-17 5
2 10 2019-04-17 6
3 10 2019-05-17 7
The output would be :-
TempID CustID RODate Operation
1 10 2019-03-17 0
2 10 2019-04-17 3
3 10 2019-05-17 7

Answer 2

--Change the value of #OperationsToBeDeducted, to see different results
declare #OperationsToBeDeducted int
declare #OperationsRemaining int
declare #RODate date
set #OperationsToBeDeducted = 4
declare #TempID int
set #TempID = 1
DROP TABLE IF EXISTS #TempOperation
create table #TempOperation
(
TempID INT IDENTITY(1,1) NOT NULL PRIMARY KEY,
CustID INT NOT NULL,
RODate DATE NULL,
Operation INT NULL
);
insert into #TempOperation (CustID,RODate,Operation)
values
(10,DATEADD(month, -3, getdate()),2),
(10,DATEADD(month, -2, getdate()), 2),
(10,DATEADD(month, -1, getdate()),3)
DROP TABLE IF EXISTS #TempOperation2
create table #TempOperation2
(
TempID INT IDENTITY(1,1) NOT NULL PRIMARY KEY,
CustID INT NOT NULL,
RODate DATE NULL,
Operation INT NULL
);
insert into #TempOperation2 select CustID,RODate, Operation from #TempOperation
select * from #TempOperation2 order by RODate asc
declare #maxID int;
select #maxID = max(TempID) from #TempOperation2
while (#TempID <= #maxID)
begin
set #OperationsRemaining = 0
select #OperationsRemaining = Operation, #RODate = RODate from #TempOperation2 where TempID = #TempID
if(#OperationsToBeDeducted is not null and #OperationsRemaining is not null and
#OperationsRemaining > 0 and #OperationsRemaining > #OperationsToBeDeducted)
begin
update #TempOperation set Operation = #OperationsRemaining - #OperationsToBeDeducted where TempID = #TempID
set #OperationsToBeDeducted = 0
end
else if(#OperationsToBeDeducted is not null and #OperationsRemaining is not null and
#OperationsRemaining > 0 and #OperationsRemaining <= #OperationsToBeDeducted)
begin
set #OperationsToBeDeducted = #OperationsToBeDeducted - #OperationsRemaining
update #TempOperation set Operation = #OperationsRemaining - #OperationsRemaining where TempID = #TempID
end
SET #TempID = #TempID + 1
end
select * from #TempOperation order by RODate asc
DROP TABLE #TempOperation
DROP TABLE #TempOperation2