How use the query to find unit stock?

[Guest]

How can I query in order to find the inventory unit? If my purchsing units
and sale units are in seperate tables.
I can use query to find the purchased unit alone. I can use query to find
the sale unit alone as well. In order to find inventory stock, I can not use
query to find purchased and saled unit at the same query.
Could you tell me how to use one query to find both of purchased unit and
saled units?

 

[Guest]

SELECT ItemID, Item, UOM from tPurchasing
UNION
SELECT ItemID, Item, UOM from tSales