Merchant - Finding the most valued shoppers

The marketing team at dimestore wants to e-mail special discount coupons to the top 10 loyal shoppers.

List the top 10 shoppers based on the total amount spent

ScreenShot

    SELECT  customer.firstName, 
        customer.lastName, 
        customer.emailAddress,
        SUM(items.count) purchaseCount, 
        ROUND(SUM(product.unitPrice * items.count))  totalSpent 
    FROM purchases UNNEST purchases.lineItems AS items 
    JOIN product ON KEYS items.product JOIN customer ON KEYS purchases.customerId 
    GROUP BY customer 
    ORDER BY totalSpent DESC LIMIT 10