Try (not tested)

SELECT Cust, QtyIn, QtyOut, QtyIn-QtyOut As QtyDiff
FROM (
	SELECT Cust, SUM(qin.qty) AS QtyIn, SUM(qout.qty) AS QtyOut
		FROM Customers cs
			LEFT JOIN StandsIn qin ON qin.cust = cs.cust
			LEFT JOIN StandsOut qout ON qout.cust = cs.cust
		GROUP BY Cust
	) dt1
WHERE QtyOut > QtyIn

>I am trying to write a SQL Statement that has three tables. I am looking at WIRE STANDS being received from various customers WITHOUT WIRE on them into our Company and a certain number being sent out to customers WITH WIRE on them.
>
>We have the following tables:
>
>CUSTOMERS-Holds all of our customers company names and CUST ID.
>STANDSIN - with a field called Qty for stands received from customers
>STANDSOUT- also with a field called Qty for stands shipped out
>
>Customer has a CUST field and is indexed as CUST.
>StandsIn and StandOut also have CUST as one of their related fields to the CUSTOMER table.
>
>I want to end up with a report GROUPED by CUSTOMERS showing stands Received and Stands shipped out as followed:
>

>NAME OF CUSTOMER   QTY Recv'd    QTY Sent Out   Difference (Recv'd-Shipped)
>CUSTOMER_A         13            23             -10
>CUSTOMER_B         98            58             40
>CUSTOMER_C         112           140            -28
>CUSTOMER_D         1000          980            20
>

>What we are trying to do is to focus on the customers who have not been returning our stands, so that if we see a negative number, we know that that customer has not been returning our WIRE STANDS and can then focus on them.
>
>I tried a regular UNION SQL Statement, but that didn't seem right. Would this require more of a LEFT OUTER JOIN type of statement?