SQL- Date Diff- # of week in each month between two date periods - sql

Question

Problem: Display in columns the number of weeks in each month between two date periods (out to three months is fine for now). If possible, from the current day (Dynamic)
Where I currently am:
SELECT Q3.[Begin Date]
,Q3.[End Date]
,Q3.Diff_in_Year
,sum(CASE
WHEN Q3.Year_Counter = 0
THEN datediff(mm, Q3.y_start, Q3.y_end) + 1
ELSE 0
END) Y1
,sum(CASE
WHEN Q3.Year_Counter = 1
THEN datediff(mm, Q3.y_start, Q3.y_end) + 1
ELSE 0
END) Y2
,sum(CASE
WHEN Q3.Year_Counter = 2
THEN datediff(mm, Q3.y_start, Q3.y_end) + 1
ELSE 0
END) Y3
,sum(CASE
WHEN Q3.Year_Counter = 3
THEN datediff(mm, Q3.y_start, Q3.y_end) + 1
ELSE 0
END) Y4
,sum(CASE
WHEN Q3.Year_Counter = 4
THEN datediff(mm, Q3.y_start, Q3.y_end) + 1
ELSE 0
END) Y5
,sum(CASE
WHEN Q3.Year_Counter = 5
THEN datediff(mm, Q3.y_start, Q3.y_end) + 1
ELSE 0
END) Y6
,sum(CASE
WHEN Q3.Year_Counter = 6
THEN datediff(mm, Q3.y_start, Q3.y_end) + 1
ELSE 0
END) Y7
,sum(CASE
WHEN Q3.Year_Counter = 7
THEN datediff(mm, Q3.y_start, Q3.y_end) + 1
ELSE 0
END) Y8
,sum(CASE
WHEN Q3.Year_Counter = 8
THEN datediff(mm, Q3.y_start, Q3.y_end) + 1
ELSE 0
END) Y9
,sum(CASE
WHEN Q3.Year_Counter = 9
THEN datediff(mm, Q3.y_start, Q3.y_end) + 1
ELSE 0
END) Y10
FROM (
SELECT Q1.[Begin Date]
,Q1.[End Date]
,Q1.years Diff_in_Year
,Q2.number AS Year_Counter
,(
CASE
WHEN Q2.number = 0
THEN Q1.[Begin Date]
ELSE dateadd(yy, datediff(yy, 0, dateadd(yy, q2.number, q1.[Begin Date])), 0)
END
) AS y_Start
,(
CASE
WHEN ((Q1.years - 1) = Q2.number)
THEN Q1.[End Date]
ELSE DATEADD(yy, DATEDIFF(yy, 0, dateadd(yy, q2.number + 1, q1.[Begin Date]) + 1), - 1)
END
) AS y_End
,Year(Q1.[Begin Date]) + Q2.number YearInYYYY
FROM (
SELECT [Begin Date]
,[End Date]
,DATEDIFF(year, [Begin Date], [End Date]) + 1 AS years
FROM my dates
) Q1
INNER JOIN master..spt_values Q2 ON Q2.type = 'P'
AND Q2.number < Q1.years
) Q3
GROUP BY Q3.[Begin Date]
,Q3.[End Date]
,q3.Diff_in_Year
How the current code works: Given a date range, the number of months in each year between two dates. IE 1/1/2014 - 1/18/2015 would give two columns "2014" and 2015" the value of 2014 is 12 and the value of 2015 is 1 signifying that there are 13 months between the specified dates.
What I am hoping to achieve is something similar to
Start Date End Date Month 1 Month 2 Month 3
-----------------------------------------------------
1/1/2014 3/8/2014 4 4 1

Answer 1

Dynamic SQL solutions aside (search for dynamic pivot in TSQL), I whipped up a couple of answers. Since your question is unclear whether you want weeks or months, I put together a quick one for each.
Months Example Here:
declare #startdate date = '1/1/2014', #enddate date = '3/1/2015'
select p.*
from (
select #startdate as StartDate, #enddate as EndDate, right(convert(varchar,(dateadd(mm,RowID-1,#startdate)),105),4) [Group]
from (
select *, row_number()over(order by name) as RowID
from master..spt_values
) d
where d.RowID <= datediff(mm, #startdate, #enddate)
) t
pivot (
count([Group]) for [Group] in (
[2014],[2015]
)
) p
Weeks Example Here:
declare #startdate date = '1/1/2014', #enddate date = '3/1/2015'
select p.*
from (
select #startdate as StartDate, #enddate as EndDate, right(convert(varchar,(dateadd(ww,RowID-1,#startdate)),105),7) [Group]
from (
select *, row_number()over(order by name) as RowID
from master..spt_values
) d
where d.RowID <= datediff(ww, #startdate, #enddate)
) t
pivot (
count([Group]) for [Group] in (
[01-2014]
, [02-2014]
, [03-2014]
, [04-2014]
, [05-2014]
, [06-2014]
, [07-2014]
, [08-2014]
, [09-2014]
, [10-2014]
, [11-2014]
, [12-2014]
, [01-2015]
, [02-2015]
, [03-2015]
)
) p