(Newbie) Join problem.

[SQL-Newbie]

Hi,
I'm new to SQL trying to use a base that was set up by another firm.
I can't get it to do what I want and I don't know if it's due to my
ignorance or bad table design ...

I have three tables
Sales
containing ProdID and Amounts

Products
containing ProdID and ProdTypeID and
ProdSubTypeID

Product-types
containing ProdTypeID and ProdTypeIDLabel and
ProdSubTypeID and ProdSubTypeIDLa bel

I have to do some stats in Excel or in Crystal
totalling Amounts
grouped by ProductTypeLabe l and
grouped by ProductSubTypeL abel.

Here's what I can do...
------------------------------
Using ProdTypeID, I can join Product-Types to Products,
and
using ProdID, I can join Products to Sales
and get a sum of amounts grouped by ProductTypeLabe l. OK.

Also,
Using ProdTypeID, I can join Product-Types to Products,
and
using ProdID, I can join Products to Sales
and get a sum of amounts grouped by ProductSubTypeL abel. OK.


Here's what I can't do...
------------------------------
Get both (i.e. ProductTypeLabe l and ProductSubTypeL abel) in the same report
and the correct amounts.

I have found a solution but it involves modifying the tables.
I create a new field with the Type and SubType concatenated in Products and
also in Product-Types (ProductTypeGlo bal) and then join on that.
So,
Using ProductTypeGlob al, I can join Product-Types to Products,
and
using ProdID, I can join Products to Sales
and get a sum of amounts
grouped by ProductTypeLabe l
AND
grouped by ProductSubTypeL abel
OK.

Is there some way to create the correct joins in SQL without creating the
new field?

Thanks

SQL Newbie.