SQL split number over date range - sql

Question

I have a table with, for example this data
ID |start_date |end_date |amount
---|------------|-----------|-------
a1 |2013-12-01 |2014-03-31 |100
Iwant to have a query that split the dates so I have the amount splitted out over the year like this :
ID |org_start_date |org_end_date |new_start_date |new_end_date |amount
---|----------------|---------------|----------------|----------------|-------
a1 |2013-12-01 |2014-03-31 |2013-12-01 |2013-12-31 |25
a1 |2013-12-01 |2014-03-31 |2014-01-01 |2014-03-31 |75
The 25 in 2013 is because 2013 has one month and 75 in 2014 because this has 3 months
Is there a way to do this in T-SQL?
Thx in advance!

Answer 1

Use spt_values table to create a calendar table, then join to your table to split date range into any part you want.
If split by year and divide amount by months you could:
with dates as
(
select number,DATEADD(day,number,'20130101') as dt
from master..spt_values
where number between 0 and 1000 AND TYPE='P'
)
select
m.start_date as org_start_date,
m.end_date as org_end_date,
min(d.dt) as new_start_date,
max(d.dt) as new_end_date,
m.amount*count(distinct month(d.dt))/(datediff(month,m.start_date,m.end_date)+1) as amount
from
MonthSplit m
join
dates d
on
d.dt between m.start_date and m.end_date
group by
m.start_date, m.end_date, year(d.dt),m.amount
Here is the SQL FIDDLE DEMO.

Answer 2

Here is a solution using a numbers table:
SQL Fiddle Example
DECLARE #STARTYR INT = (SELECT MIN(YEAR([Start Date])) FROM Table1)
DECLARE #ENDYR INT = (SELECT MAX(YEAR([End Date])) FROM Table1)
SELECT [Id]
, #STARTYR + Number AS [Year]
, CASE WHEN YEAR([Start Date]) < #STARTYR + Number
THEN DATEADD(YEAR, #STARTYR - 1900 + Number,0)
ELSE [Start Date] END AS [Start]
, CASE WHEN YEAR([End Date]) > #STARTYR + Number
THEN DATEADD(YEAR, #STARTYR - 1900 + Number + 1,0)
ELSE [End Date] END AS [End]
, DATEDIFF(MONTH,CASE WHEN YEAR([Start Date]) < #STARTYR + Number
THEN DATEADD(YEAR, #STARTYR - 1900 + Number,0)
ELSE [Start Date] END
,CASE WHEN YEAR([End Date]) > #STARTYR + Number
THEN DATEADD(YEAR, #STARTYR - 1900 + Number + 1,0)
ELSE DATEADD(MONTH,DATEDIFF(MONTH,0,DATEADD(MONTH,1,[End Date])),0) END) AS [Months]
, DATEDIFF(MONTH,[Start Date],[End Date]) + 1 [Total Months]
, ([Amount] / (DATEDIFF(MONTH,[Start Date],[End Date]) + 1))
*
DATEDIFF(MONTH,CASE WHEN YEAR([Start Date]) < #STARTYR + Number
THEN DATEADD(YEAR, #STARTYR - 1900 + Number,0)
ELSE [Start Date] END
,CASE WHEN YEAR([End Date]) > #STARTYR + Number
THEN DATEADD(YEAR, #STARTYR - 1900 + Number + 1,0)
ELSE DATEADD(MONTH,DATEDIFF(MONTH,0,DATEADD(MONTH,1,[End Date])),0) END) AS [Proportion]
FROM Numbers
LEFT JOIN Table1 ON YEAR([Start Date]) <= #STARTYR + Number
AND YEAR([End Date]) >= #STARTYR + Number
WHERE Number <= #ENDYR - #STARTYR

Answer 3

I don't have a ready made SQL for you but just a thought to solve this problem. If you have some experience with SQL it won't be hard to express it in SQL.
You could do this by defining a reference table for the months that are between your begin and end date:
ID | month | year | month start | month end | count |
-----------------------------------------------------------------------------
1001 | dec-2013 | 2013 | 1-12-2013 | 31-12-2013 | 1 |
1001 | jan-2014 | 2014 | 1-1-2014 | 31-1-2014 | 1 |
1001 | feb-2014 | 2014 | 1-2-2014 | 28-2-2014 | 1 |
1001 | mar-2014 | 2014 | 1-3-2014 | 31-3-2014 | 1 |
Maybe you already have such a time ref table in your DWH.
When you join (with a between statement) your table with the record that contains the start and end date per row, with this reference table, you'll have the split from 1 row to the number of months contained in the range correct. The count column will help you to get the split ratio per year right by grouping over the year afterwards (like : 1/4 for 2013 and 3/4 for 2014). You'll have to apply the ratio to the field 'amount' that you want to split up.

Answer 4

It's very similar to this question:
Split date range into one row per month in sql server
Although you are doing grouping by year, so based on that answer you can modify it to do what you want by adding MIN, MAX to your date values and grouping by the YEAR():
SQL Fiddle Demo
Schema Setup:
CREATE TABLE MonthSplit
([ID] varchar(2), [start_date] datetime, [end_date] datetime, [amount] int)
;
INSERT INTO MonthSplit
([ID], [start_date], [end_date], [amount])
VALUES
('a1', '2013-12-01 00:00:00', '2014-03-31 00:00:00', 100),
('a2', '2013-10-01 00:00:00', '2015-05-01 00:00:00', 400)
;
Recursive CTE to group by Year:
WITH cte AS
(SELECT ID
, start_date
, end_date
, start_date AS from_date
, DATEADD(day, day(start_date)* -1 + 1, start_date) AS first_of_month
FROM MonthSplit
UNION ALL
SELECT ID
, start_date
, end_date
, DATEADD(month,1,first_of_month)
, DATEADD(month,1,first_of_month)
FROM cte
WHERE DATEADD(month,1,from_date) < end_date
)
SELECT ID as ID,
min(start_date) as org_start_date,
min(end_date) as org_end_date,
min(from_date) AS new_start_date,
CASE when max(end_date) < DATEADD(month,1,max(first_of_month)) THEN
max(end_date)
ELSE
DATEADD(day, -1, DATEADD(month,1,max(first_of_month)))
END AS new_end_date
FROM cte
group by year(from_date), ID
Results:
| ID | ORG_START_DATE | ORG_END_DATE | NEW_START_DATE | NEW_END_DATE |
|----|-------------------|----------------|-------------------|-------------------|
| a1 | December, 01 2013 | March, 31 2014 | December, 01 2013 | December, 31 2013 |
| a1 | December, 01 2013 | March, 31 2014 | January, 01 2014 | March, 31 2014 |
| a2 | October, 01 2013 | May, 01 2015 | October, 01 2013 | December, 31 2013 |
| a2 | October, 01 2013 | May, 01 2015 | January, 01 2014 | December, 31 2014 |
| a2 | October, 01 2013 | May, 01 2015 | January, 01 2015 | April, 30 2015 |