Updating SQl rows on the basis of previous row val

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Updating SQl rows on the basis of previous row val

Author

Topic

mehra.abhinav88
Starting Member

1 Post

Posted - 2013-04-03 : 02:20:24

Hi,

I need urgent help... I want to update row value which have some portion from previous row value. ( Basically I need to find carry over effect).

I am using While loop or cursor to do the same but it is taking alot of time as the update statement runs number of rows times.

Please suggest me a good efficient way to find out carry over effect. Below is the example of dataset with 0.2 carry over effect.

WeekNumber Var1 carry_over_effect_0.2
1 10 10
2 30 30+0.2*10
3 80 80+(30+0.2*10)*0.2

and so on

Thanks
Abhinav Mehra
mehra.abhinav88@gmail.com

visakh16
Very Important crosS Applying yaK Herder

52326 Posts

Posted - 2013-04-03 : 02:26:15

try a recursive CTE approach


;With YourCTEName
AS
(
SELECT WeekNumber,Var1,Var1 AS carry_over_effect_0.2
FROM Table
WHERE WeekNumber=1

UNION ALL

SELECT t.WeekNumber,t.Var1,t.Var1 + 0.2 * c.carry_over_effect_0.2
FROM Table t
JOIN YourCTEName c
ON c.WeekNumber = t.WeekNumber -1
)

SELECT *
FROM YourCTENAme

OPTION (MAXRECURSION 0)

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