How to duplicate data in sql with conditions - sql

Question

I havea table as table_A . table_A includes these columns
-CountryName
-Min_Date
-Max_Date
-Number
I want to duplicate data with seperating by months. For example
Argentina | 2015-01-04 | 2015-04-07 | 100
England | 2015-02-08 | 2015-03-11 | 90
I want to see a table as this (Monthly seperated)
Argentina | 01-2015 | 27 //(days to end of the min_date's month)
Argentina | 02-2015 | 29 //(days full month)
Argentina | 03-2015 | 31 //(days full month)
Argentina | 04-2015 | 7 //(days from start of the max_date's month)
England | 02-2015 | 21 //(days)
England | 03-2015 | 11 //(days)
I tried too much thing to made this for each records. But now my brain is so confusing and my project is delaying.
Does anybody know how can i solve this. I tried to duplicate each rows with datediff count but it is not working
WITH cte AS (
SELECT CountryName, ISNULL(DATEDIFF(M,Min_Date ,Max_Date )+1,1) as count FROM table_A
UNION ALL
SELECT CountryName, count-1 FROM cte WHERE count>1
)
SELECT CountryName,count FROM cte

Answer 1

-Generate all the dates between min and max dates for each country.
-Then get the month start and month end dates for each country,year,month.
-Finally get the date differences of the month start and month end.
WITH cte AS (
SELECT Country, min_date dt,min_date,max_date FROM t
UNION ALL
SELECT Country, dateadd(dd,1,dt),min_date,max_date FROM cte WHERE dt < max_date
)
,monthends as (
SELECT country,year(dt) yr,month(dt) mth,max(dt) monthend,min(dt) monthstart
FROM cte
GROUP BY country,year(dt),month(dt))
select country
,cast(mth as varchar(2))+'-'+cast(yr as varchar(4)) yr_month
,datediff(dd,monthstart,monthend)+1 days_diff
from monthends
Sample Demo
EDIT: Another option would be to generate all the dates once (the example shown here generates 51 years of dates from 2000 to 2050) and then joining it to the table to get the days by month.
WITH cte AS (
SELECT cast('2000-01-01' as date) dt,cast('2050-12-31' as date) maxdt
UNION ALL
SELECT dateadd(dd,1,dt),maxdt FROM cte WHERE dt < maxdt
)
SELECT country,year(dt) yr,month(dt) mth, datediff(dd,min(dt),max(dt))+1 days_diff
FROM cte c
JOIN t on c.dt BETWEEN t.min_date and t.max_date
GROUP BY country,year(dt),month(dt)
OPTION (MAXRECURSION 0)

Answer 2

I think you have the right idea. But you need to construct the months:
WITH cte AS (
SELECT CountryName, Min_Date as dte, Min_Date, Max_Date
FROM table_A
UNION ALL
SELECT CountryName, DATEADD(month, 1, dte), Min_Date, Max_Date
FROM cte
WHERE dte < Max_date
)
SELECT CountryName, dte
FROM cte;
Getting the number of days in the month is a bit more complicated. That requires some thought.
Oh, I forgot about EOMONTH():
select countryName, dte,
(case when dte = min_date
then datediff(day, min_date, eomonth(dte)) + 1
when dte = max_date
then day(dte)
else day(eomonth(dte))
end) as days
from cte;

Answer 3

Using a Calendar Table makes this stuff pretty easy. RexTester: http://rextester.com/EBTIMG23993
begin
create table #enderaric (
CountryName varchar(16)
, Min_Date date
, Max_Date date
, Number int
)
insert into #enderaric values
('Argentina' ,'2015-01-04' ,'2015-04-07' ,'100')
, ('England' ,'2015-02-08' ,'2015-03-11' ,'90')
end;
-- select * from #enderaric
--*/"
declare #FromDate date;
declare #ThruDate date;
set #FromDate = '2015-01-01';
set #ThruDate = '2015-12-31';
with x as (
select top (cast(sqrt(datediff(day, #FromDate, #ThruDate)) as int) + 1)
[number]
from [master]..spt_values v
)
/* Date Range CTE */
,cal as (
select top (1+datediff(day, #FromDate, #ThruDate))
DateValue = convert(date,dateadd(day,
row_number() over (order by x.number)-1,#FromDate)
)
from x cross join x as y
order by DateValue
)
select
e.CountryName
, YearMonth = convert(char(7),left(convert(varchar(10),DateValue),7))
, [Days]=count(c.DateValue)
from #enderaric as e
inner join cal c on c.DateValue >= e.min_date
and c.DateValue <= e.max_date
group by
e.CountryName
, e.Min_Date
, e.Max_Date
, e.Number
, convert(char(7),left(convert(varchar(10),DateValue),7))
results in:
CountryName YearMonth Days
---------------- --------- -----------
Argentina 2015-01 28
Argentina 2015-02 28
Argentina 2015-03 31
Argentina 2015-04 7
England 2015-02 21
England 2015-03 11
More about calendar tables:
Aaron Bertrand - Generate a set or sequence without loops
generate-a-set-1
generate-a-set-2
generate-a-set-3
David Stein - Creating a Date Table/Dimension on SQL 2008
Michael Valentine Jones - F_TABLE_DATE