Sql function that returns months and number of days in month in date range

Trying to write a sql table function that will return month and number of days in the month with input parameters of start date and end date

For example, if the input date is 03/22/2015 and end date is 04/12/2015

Would like table returned to be

Month  DaysInMonth
3            10
4             12
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Mike EghtebasDatabase and Application DeveloperCommented:
Create function fn_YearMonthDays(@dt1 date, @dt2 date) returns table
select 'Start: ' As StartStop
     , datePart(Year,@dt1) As Y
     , datePart(Month,@dt1) As m
	 , datePart(Day,@dt1) As d
Union select 'Stop: ' As StartStop
     , datePart(Year,@dt2) As Y
     , datePart(Month,@dt2) As m
	 , datePart(Day,@dt2) As d

-- test
declare @dt1 date = '03/22/2015';
declare @dt2 date = '04/12/2015';
Select * from fn_YearMonthDays(@dt1, @dt2);

Open in new window


StartStop      Y      m      d
Start:       2015      3      22
Stop:       2015      4      12

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johnnyg123Author Commented:
johnnyg123Author Commented:

I think I accepted a bit prematurely

I mentioned that I wanted days and months for all months in the period

If I try

-- test
declare @dt1 date = '03/22/2015';
declare @dt2 date = '05/12/2015';
Select * from fn_YearMonthDays(@dt1, @dt2);

I get

StartStop      Y      m      d
Start:       2015      3      22
Stop:       2015      5      12

In this scenario I would want

StartStop      Y      m      d
Start:       2015      3      22
                2015       4      30
Stop:       2015      5      12
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Mike EghtebasDatabase and Application DeveloperCommented:
re:> I mentioned that I wanted days and months for all months in the period

I read the original question again but I didn't see all months.

I am sure this is what you had in mind but you have stated a bit differently. You always can add a new question asking for the changes.

johnnyg123Author Commented:
No worries I figured it out
johnnyg123Author Commented:
In case any one is following this post

here is what I figured out

(added some additional functionality to allocate cost)

ALTER FUNCTION [dbo].[fnAllocateCampaignCosts] (@FromDate DATETIME,@EndDate DATETIME,@Amount Decimal(18,2))
RETURNS @tblResults TABLE([Year] INT, [Month] INT, [Days] INT,AllocationAmount decimal(18,2))
   DECLARE @Months INT
   Declare @AmountPerDay decimal(18,2)

      DECLARE      @StartDay INT, @StartMonth INT, @StartYear INT, @EndDay INT, @EndMonth INT, @EndYear INT
      SELECT      @StartDay = DAY(@FromDate), @StartMonth = MONTH(@FromDate), @StartYear = YEAR(@EndDate),
                  @EndDay = DAY(@EndDate), @EndMonth = MONTH(@EndDate), @EndYear = YEAR(@EndDate)

      DECLARE      @LastDayOfMonth INT

      WHILE (@StartYear < @EndYear) OR (@StartMonth <= @EndMonth AND @StartYear = @EndYear)
            -- Find last Day of current Month
            SELECT      @LastDayOfMonth = CASE
                              WHEN @StartYear = @EndYear AND @StartMonth = @EndMonth THEN @EndDay
                              WHEN @StartMonth IN (1, 3, 5, 7, 8, 10, 12) THEN 31
                              WHEN @StartMonth IN (4, 6, 9, 11) THEN 30
                              ELSE CASE
                                    WHEN (@StartYear % 4) = 0 THEN 29 ELSE 28

            -- Calculate number of Days of current Month and insert to result table
            INSERT      @tblResults([Year] , [Month], [Days])
            VALUES      (
                  @LastDayOfMonth - @StartDay + 1
            -- Next month
            SELECT      @StartYear = CASE WHEN @StartMonth = 12 THEN @StartYear + 1 ELSE @StartYear END,
                        @StartMonth = CASE WHEN @StartMonth = 12 THEN 1 ELSE @StartMonth + 1 END,
                        @StartDay = 1 -- Reset to 1 for next Month

      --Select * from @tblResults where month = '02'

      --SELECT  @Days = (Select days from @tblResults where month = @Month)
 --Return  @Days

      -- Select result

      set @Days = (Select sum(days) from @tblResults)
      set @months = (Select count(month) from @tblResults)

      set @AmountPerDay = @Amount/@Days

      Update @tblResults  set AllocationAmount =  case when @months = 1 then @Amount Else  @AmountPerDay * [Days] end

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Microsoft SQL Server 2008

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