Using multiple JOINS. SUM() producing wrong value

Question

I am getting some basic invoice information in a SQL query and figuring the Order Total and Payment Totals in the same query. Here is what I have thus far:

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Answer 1

my guess is that the payment is $10 and there are two items in the order (orderitems table). if that's the case, try using a GROUP BY on the orders/customers/orderstatus fields.