DATEDIFF inconsistencies when report range crosses years

Question

Hi folks -
I have a requirement for a software metering report that provides prompted month ranges for usage activity - for what good reason, I still have not been told.  At any rate cannibalized a few reports to arrive at the following.  When I check
the output of the number of months chosen, it seems to work fine when I use ranges in the same year, but when I choose 12/2013-6/2014 for example I get larger numbers that don't total up to the number of months.  Can anyone please take a look at my query
and see if I am missing something?  Maybe I'm just not understanding DATEDIFF and am not giving it the proper values.  Sorry - we're still on 2007 and I know many have moved to 2012.  Also I notice when I give it an out of bounds parameter,
like ending date of 7/14, for which I don't have any summarized data yet, it returns nothing.  How could I make it revert to the previous month for which data exist? 
Thanks for any help!!!
declare @TimeKey int
declare @months float
declare @endTimeKey int
set @TimeKey=100*@Year+@Month
set @endTimeKey=100*@endYear+@EndMonth
select @TimeKey
select @endTimeKey
select @months=DATEDIFF(d,@timekey,@endTimeKey)
from v_SummarizationInterval where TimeKey>=@TimeKey and TimeKey< @endTimeKey
select @months
if IsNULL(@months,0) > 0
select
sys.Netbios_Name0, mf.productname, MAX(mf.meteredfileversion) as 'Product Version',
sys.User_Name0, v_GS_SYSTEM_CONSOLE_USAGE_MAXGROUP.topconsoleuser0,v_R_User.displayName0 as 'User Display Name',
MAX(v_RA_User_UserOUName.User_OU_Name0) as 'User OU', v_R_User.unique_user_name0 as 'FQ User Name',
v_R_User.telephonenumber0 as 'Telephone', v_R_User.mail0 as 'E-Mail',
DATEADD(ss,@__timezoneoffset,MAX(mus.LastUsage)) as LastUsage,
SUM(UsageCount) + SUM(TSUsageCount) as C021,
ROUND((SUM(UsageCount) + SUM(TSUsageCount))/(@months*30),2) as C022,
ROUND(SUM(UsageTime)/60.0,2) as C023,
ROUND(SUM(UsageTime)/60.0/(SUM(UsageCount) + SUM(TSUsageCount)),2) as C024,
ROUND(SUM(UsageTime)/60.0/(@months*30),2) as C025
from v_R_System sys
join v_MonthlyUsageSummary mus on sys.ResourceID=mus.ResourceID
join v_MeteredFiles mf on mus.FileID=mf.MeteredFileID
left join v_RA_System_SMSInstalledSites inst on sys.ResourceID=inst.ResourceID
full join v_R_User on sys.user_name0 = v_R_User.user_name0
left outer join v_RA_User_UserOUName on v_RA_User_UserOUName.ResourceID = v_R_User.ResourceID
left join v_GS_SYSTEM_CONSOLE_USAGE_MAXGROUP on v_GS_SYSTEM_CONSOLE_USAGE_MAXGROUP.ResourceID = sys.ResourceID
where mf.ProductName = 'Adobe Acrobat'
and mus.TimeKey =@endTimeKey
group by sys.Netbios_Name0, sys.User_Name0, v_R_User.displayName0, v_R_User.unique_user_name0,
v_R_User.telephonenumber0, v_R_User.mail0, mf.productname, V_GS_SYSTEM_CONSOLE_USAGE_MAXGROUP.topconsoleuser0
having SUM(UsageCount) + SUM(TSUsageCount) > 0
order by sys.Netbios_Name0
--Month Prompt
begin
if (@__filterwildcard = '')
select distinct DATEPART(month,IntervalStart) as Month, DATEPART(year,IntervalStart) as Year from v_SummarizationInterval order by DATEPART(year,IntervalStart), DATEPART(month,IntervalStart)
else
select distinct DATEPART(month,IntervalStart) as Month, DATEPART(year,IntervalStart) as Year from v_SummarizationInterval
WHERE DATEPART(month,IntervalStart) like @__filterwildcard
order by DATEPART(year,IntervalStart), DATEPART(month,IntervalStart)
end
--Year Prompt
begin
if (@__filterwildcard = '')
select distinct DATEPART(year,IntervalStart) as Year from v_SummarizationInterval order by DATEPART(year,IntervalStart)
else
select distinct DATEPART(year,IntervalStart) as Year from v_SummarizationInterval
WHERE DATEPART(year,IntervalStart) like @__filterwildcard
order by DATEPART(year,IntervalStart)
end
--EndMonth and EndYear prompts mirror the above

Answer 1

I’m cleaning up old, post did you figure this out yet, if so how?
Garth Jones | My blogs: Enhansoft and
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@GarthMJ