How can I avoid cursor in this situation? - sql

Question

I have a table with following columns
Period, WIP_Close, WIP_Open, WIP_Add, WIP_Minus.
I need to update
WIP_Open = WIP_Close for previous period
and then
update WIP_Close = WIP_Open + WIP_Add - WIP_Minus.
Currently I am using cursor as follows:
declare y_curs cursor for select distinct period
from abc
order by period
declare #period as int
declare #old_period as int
set #old_period = 0
open y_curs
fetch y_curs into #period
while ##fetch_status = 0
begin
update f set f.wip_open = isnull(f1.wip_close,0)
from abc f join abc f1 on 1=1
where f.period = #period and f1.period=#old_period
update abc set wip_close = (isnull(wip_open,0) + wip_add - wip_minus) where period = #period
set #old_period = #period
fetch y_curs into #period
end
close y_curs
deallocate y_curs
This is working fine and giving correct result, however due to having more than 5 million records, it takes almost an hour to process.
Is there a better way where I can avoid cursor for better performance?
Thanks for any suggestions.
Regards

Answer 1

Sorry i don't have data to test this out. Setup a sample table and give it a try.
But maybe something like this:
WITH abc_Order (n,period,WIP_Close,WIP_Open,WIP_Add,WIP_Minus) AS (
select
ROW_NUMBER() OVER(
ORDER BY
period
) n,
n,period,WIP_Close,WIP_Open,WIP_Add,WIP_Minus
from abc
)
update curr
set
WIP_Open = prev.WIP_Close,
WIP_Close = prev.WIP_Close + curr.WIP_Add - curr.WIP_Minus
from abc_Order curr
inner join abc_Order prev on
curr.n = prev.n+1

Answer 2

Lets make some test data
DECLARE #MyTable TABLE
(
Period int IDENTITY,
WIP_Open int,
WIP_Close int,
WIP_Add int,
WIP_Minus int
)
the first record has the default opening data set.
INSERT INTO #MyTable
( WIP_Open, WIP_ADD, WIP_Minus )
VALUES
( 10, 1, 2 )
Now we have some plus / minus from inventory being added / sold
INSERT INTO #MyTable
( WIP_Add, WIP_Minus )
VALUES
( 2, 1 ),
( 5, 3 ),
( 6, 1 ),
( 1, 7 );
Now lets sum up all of the changes along with the original record to see the running total and get the closing for each record.
WITH T AS
(
SELECT
Period,
WIP_Open,
WIP_Add,
WIP_Minus,
SUM(ISNULL(WIP_Open, 0) + WIP_Add - WIP_Minus) OVER (ORDER BY Period) RunningWipClose
FROM #MyTable
)
SELECT * FROM T
here is the output:
Period WIP_Open WIP_Add WIP_Minus RunningWipClose
1 10 1 2 9
2 NULL 2 1 10
3 NULL 5 3 12
4 NULL 6 1 17
5 NULL 1 7 11
After this, you use lag function to set the null opens with the prev close.

Answer 3

Input -
period WIP_Close WIP_Open WIP_Add WIP_Minus
1 1 1 1 10
2 8 3 7 5
3 6 4 9 15
Output-
period WIP_Close WIP_Open WIP_Add WIP_Minus
1 1 1 1 10
2 3 1 7 5
3 -3 3 9 15
I guess you want to solve above problem.
Here is the solution.Let me know if you are not able to understand this.
SELECT * INTO #T
FROM
(
SELECT 1 period, 1 WIP_Close, 1 WIP_Open, 1 WIP_Add, 10 WIP_Minus UNION ALL
SELECT 2 period, 8 WIP_Close, 3 WIP_Open, 7 WIP_Add, 5 WIP_Minus UNION ALL
SELECT 3 period, 6 WIP_Close, 4 WIP_Open, 9 WIP_Add, 15 WIP_Minus ) TAB
SELECT * FROM #T
DECLARE #TopC INT = (SELECT TOP 1 WIP_Close FROM #T)
DECLARE #TopO INT = (SELECT TOP 1 WIP_Open FROM #T)
DECLARE #TopDIff INT = (SELECT TOP 1 WIP_Add - WIP_Minus FROM #T)
SELECT period,
#TopC + SUM(WIP_Add - WIP_Minus) OVER (ORDER BY period ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW ) - #TopDIff AS WIP_Close,
COALESCE(#TopC + SUM(WIP_Add - WIP_Minus) OVER (ORDER BY period ROWS BETWEEN UNBOUNDED PRECEDING AND 1 PRECEDING ) - #TopDIff,#TopO) AS WIP_Open,
WIP_Add,
WIP_Minus
FROM #T