Modifying the current row based on the previous row in sql server - sql-server

Question

I have a result set like this:
YearMonth Sales
201411 100
201412 100
201501 100
201502 100
201503 100
201504 100
201505 100
201506 100
201507 100
201508 100
Need to add another row with 4% more sales than the previous month. For example my Result should be
YearMonth Sales New Sales
201411 100 100.00
201412 100 104.00
201501 100 108.16
201502 100 112.49
201503 100 116.99
201504 100 121.67
201505 100 126.53
201506 100 131.59
201507 100 136.86
201508 100 142.33
Please help me to get the best way for it.

Answer 1

Got perfect answer for your requirement. It took long time to figure out. Just change the #Temp table name with your table name and verify the column names also.
DECLARE #nCurrentSale FLOAT
DECLARE #nYeatDate INT
DECLARE #nSale FLOAT
CREATE TABLE #TempNEW(YearMonth VARCHAR(10), Sales FLOAT, NewSale FLOAT)
SELECT TOP 1 #nCurrentSale = Sales FROM #Temp
ORDER BY (CAST('01/' + SUBSTRING (CAST(YearMonth AS VARCHAR), 5 , 2) + '/' + SUBSTRING (CAST(YearMonth AS
VARCHAR), 0 , 5) AS DATETIME)) ASC
DECLARE Cursor1 CURSOR FOR
SELECT YearMonth, Sales FROM #Temp
ORDER BY (CAST('01/' + SUBSTRING (CAST(YearMonth AS VARCHAR), 5 , 2) + '/' + SUBSTRING (CAST(YearMonth AS
VARCHAR), 0 , 5) AS DATETIME)) ASC
OPEN Cursor1
FETCH NEXT FROM Cursor1 INTO #nYeatDate, #nSale
WHILE ##FETCH_STATUS = 0
BEGIN
INSERT INTO #TempNEW(YearMonth, Sales, NewSale) VALUES(#nYeatDate, #nSale, CAST(#nCurrentSale AS DECIMAL(12,2)))
SET #nCurrentSale = #nCurrentSale + ((#nCurrentSale/100) * 4)
FETCH NEXT FROM Cursor1 INTO #nYeatDate, #nSale
END
CLOSE Cursor1
DEALLOCATE Cursor1
SELECT * FROM #TempNEW
Notify me with your status.

Answer 2

Yes it possible. But first you have to alter the table and add the extra column NewSales then try with this link
https://dba.stackexchange.com/questions/34243/update-row-based-on-match-to-previous-row
i think you can done it through this link
Also sql server support some "Computed Columns in SQL Server with Persisted Values"
using that you can specify the formula what you want, then the new column value will automatically created according to your formula

Answer 3

Here's two thoughts... Not super clear if I understood the use case... Also this solution will only work for SQL 2012 and up
So given the table
CREATE TABLE [dbo].[LagExample](
[YearMonth] [nvarchar](100) NOT NULL,
[Sales] [money] NOT NULL
)
First one is fairly simple and just assumes you are wanting to base the magnitude of your percentage increase on how many days came before it...
;WITH cte
as
(
SELECT YearMonth,
ROW_NUMBER() OVER (ORDER BY YearMonth) - 1 AS SalesEntry,
cast(LAG(Sales, 1,Sales) OVER (ORDER BY YearMonth) as float) as Sales
FROM LagExample
)
SELECT YearMonth,
Sales,
cast(Sales * POWER(cast(1.04 as float), SalesEntry) AS decimal(10,2)) as NewSales
FROM cte
The Second one uses a recursive CTE to calculate the value as you move along the months..
Here's a good link about recursive CTEs
http://www.codeproject.com/Articles/683011/How-to-use-recursive-CTE-calls-in-T-SQL
;with data
as
(
SELECT Lead(le.YearMonth, 1, null) OVER (ORDER BY le.YearMonth) as NextYearMonth,
cast(le.Sales as Decimal(10,4)) as Sales,
le.YearMonth
FROM LagExample le
)
,cte
as
(
SELECT *
FROM data
Where YearMonth = '201411'
UNION ALL
SELECT
data.NextYearMonth,
cast(cte.Sales * 1.04 as Decimal(10,4)) as Sales,
data.YearMonth
From cte join
data on data.YearMonth = cte.NextYearMonth
)
SELECT YearMonth, cast(Sales as Decimal(10,2))
FROM cte
order by YearMonth