Only having looked at the table structure and views available, you might try this query in a report
SELECT DiscountCouponCode, SUM(OrderTotalPriceInMainCurrency) AS TotalCouponSales
FROM View_COM_Order_Joined
LEFT OUTER JOIN COM_DiscountCoupon ON OrderDiscountCouponID = DiscountCouponID
WHERE OrderDiscountCouponID > 0
GROUP BY DiscountCouponCode
This will get all orders with a coupon code ID in an order and group the sales totals by the coupon code. You might also want to check the order status, if they have paid, etc. to ensure you are getting correct data.