Calculate a value between 2 dates [closed] - sql

Question

Closed. This question needs details or clarity. It is not currently accepting answers.
Want to improve this question? Add details and clarify the problem by editing this post.
Closed 9 years ago.
Improve this question
I got this in a table:
id dateFrom hours
1 2013-02-01 6
2 2013-04-01 8
The hours represent the hours during a month, starting at that date, valid until next record.
I need to know how to sum the hours for month between two dates.
For example if range dates are 2013-02-01 to 2013-06-01:
6hs for february +
6hs for march +
8hs for april +
8hs for may +
8hs for june
========
36 hs

Answer 1

DECLARE #startDate DATE
DECLARE #endDate DATE
SET #startDate = '20130201'
SET #endDate = '20130601'
;WITH CTE_Months AS
(
SELECT #startDate DT
UNION ALL
SELECT DATEADD(MM,1,DT) FROM CTE_Months
WHERE DATEADD(MM,1,DT) <= #endDate
)
,CTE_RN AS
(
SELECT *, ROW_NUMBER() OVER (PARTITION BY DT ORDER BY dateFrom DESC) RN
FROM CTE_Months m
LEFT JOIN Table1 t ON m.DT >= t.dateFrom
)
SELECT SUM(hours)
FROM CTE_RN WHERE RN = 1
First recursive CTE is to find gaps between two dates, second CTE using ROW_NUMBER and JOIN on actual table to find hours for each month. At the end, just sum WHERE RN=1
SQLFiddle DEMO

Answer 2

I get it. The hours represent the hours during a month, starting at that date. You then want to add things up by month.
The following uses a recursive CTE to calculate one day in each month. It then joins to your table, and chooses the most recent row before the current row. Finally, it adds up the hours:
declare #fromdate date = '2013-02-01';
declare #todate date = '2013-06-01';
with months as (
select #fromdate as thedate
union all
select DATEADD(month, 1, thedate)
from months
where DATEADD(month, 1, thedate) <= #todate
),
t as (
select 1 as id, CAST('2013-02-01' as DATE) as datefrom, 6 as hours union all
select 2, '2013-04-01', 8
)
select SUM(hours)
from (select t.*, m.thedate, ROW_NUMBER() over (partition by m.thedate order by t.datefrom desc) as seqnum
from months m join
t
on m.thedate >= t.datefrom
) t
where seqnum = 1;

Answer 3

So the problem is actually two fold here. First we need to normalise it so we get actual month,hourPermonth tuples. We need to create month increments between row n and row n+1 and give them each the hours value of the original table.
I solved it by using an inline table-valued function that you can call or cross apply with parameters.
Complete solution to test here: http://sqlfiddle.com/#!6/b7e58/1
Sample code for the function and how to call it:
CREATE FUNCTION dbo.GetSum(#startDate date,#endDate date)
RETURNS TABLE
AS RETURN
(
WITH cte as
(
SELECT #startDate as s
UNION ALL
SELECT DATEADD(month,1,s)
FROM cte WHERE s<#endDate
)
SELECT
SUM(hours) as sumHours
FROM cte
CROSS APPLY (SELECT top 1 h.hours FROM dbo.hourInterval as h WHERE h.startdate <= cte.s order by h.startdate desc) as t
)
GO
SELECT * FROM dbo.GetSum('2013-02-01','2013-06-01')