opdele datointerval i måneder

Følgende forespørgsel burde gøre tricket. CTE (WITH klausul) genererer dynamisk nogle månedsdata, som vi kan bruge til at deltage i.

declare @test table (
    userid char(1),
    project char(4),
    startdate datetime,
    enddate datetime)

insert into @test
select 'A', 'abc1', '1/1/2011', '12/31/2011'
union select 'A', 'abc2', '1/1/2011', '5/1/2011'
union select 'B', 'xyz1', '1/1/2011', '3/1/2011'

--select * from @test

;with MonthList as (
    select 
        DATEADD(month, M, '12/1/1899') as 'FirstDay',
        dateadd(day, -1, dateadd(month, M + 1, '12/1/1899')) as 'LastDay',
        DATEADD(month, M + 1, '12/1/1899') as 'FirstDayNextMonth'
    from (
        select top 3000 ROW_NUMBER() over (order by s.name) as 'M'
        from master..spt_values s) s
)

select
    t.userid, t.project, ml.FirstDay, ml.LastDay
from
    @test t
    inner join MonthList ml
        on  t.startdate < ml.FirstDayNextMonth
            and t.enddate >= ml.FirstDay