MS Access: Group by months for each month between Start Date and End Date

Question

I have these four data fields - ID, SubscriptionStartDate, SubscriptionEndDate and MonthlyCost in MS Access. Subscription Start and End Date will cover multiple months or even years, I want to sum MonthlyCost for each individual month between Start and End Date for all the IDs.

Using SQL in Access, I am looking for an output like:

Month TotalMonthlyCost

Jan-13 100000 -> total monthly cost for Jan-13, summed across all the IDs.

Feb-13 150000 -> total monthly cost for Feb-13, summed across all the IDs. ...

Answer 1

I think that you could do something like this:

select
    m.month
    ,sum(d.MonthlyCost)
from
    months as m
    inner join data as d
        on d.SubscriptionStartDate < m.endDate
        and d.SubscriptionEndDate > m.start
group by
    m.month

You would need to create the table "months" that would look like this:

   month   |    start   |   end
 'jan-13'  | 01/01/2013 | 31/01/2013
 'feb-13'  | 01/02/2013 | 28/02/2013
 'mar-13'  | 01/03/2013 | 31/03/2013

but this is saying if you are in that month at all (even for one day) then you rmonthly subscription should be added. Is that correct?

Note: i don't have access here and i cant remember if my syntax is perfect for access. (i think you need brackets in the join clauses or something)