Oh, okay. I'll give it a try. (Remember when MSFT used to be really explicit about which version of a program was installed and you could go to help>about and...

Do I seriously have to create a DSN for this to work?

Thanks Federico. I downloaded that and installed it,
I created a connection using the Source Assistant and could only connect to the database at all using the SSIS provider. But...

Please post the table definitions for the relevant tables. What you're doing sounds way harder than this should be.

Isn't it as simple as DIVIDE(COUNTROWS('OrderLineItems'),COUNTROWS('Orders')) ?

This?
SELECT SortOrder, country, colour, amount
    , DENSE_RANK() OVER (ORDER BY SortOrder) AS rn
FROM #testing
ORDER BY SortOrder
        , Country
        , Colour
        , Amount

Oh wait,...

I wouldn't back up the structure to Access. There isn't a perfect 1:1 object mapping between the two. Why not just script out all the objects so you have all...

This returns the first of the current month
SELECT DATEADD(month, DATEDIFF(month, 0, GETDATE()), 0) AS StartOfMonth

So you'd just add months to that.

Not sure if this will help at all, but here goes.
Say you create one query that calculates the Numerator (and you include the grouping column you need, so you...

In the outermost query (the first SELECT), you'd just do something like
SELECT [Aggregate1] / [Aggregate2]
FROM...

As long as the two values are correct in the source query,...