I am trying to create one view which sums orders and payments by customer. I have three tables; cust, orders and pay and they are linked by custid. All customers have at least one order and one payment.
I get incorrect results with the following code:

SELECT Cust.custid, Cust.custname, sum(orders.amt), sum(pay.payamt);
FROM cust ;
Inner Join orders on Cust.custid = Orders.custid ;
Inner Join pay on cust.custid = pay.custid;
GROUP BY Cust.custid


The following, however, does work correctly, but I want it in one view.

SELECT Cust.custid, Cust.custname, sum(orders.amt);
FROM cust ;
Inner Join orders on Cust.custid = Orders.custid ;
GROUP BY Cust.custid;
into Cursor temp

Select temp.*, sum(pay.payamt);
From Temp;
Inner Join pay on Temp.custid=pay.custid;
Group by Temp.custid

Can anyone explain what is going on and perhaps provide some help?
Thanks
Jay