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

    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 key items.product join customer key purchases.customerId 
    GROUP BY customer 
    ORDER BY totalSpent desc limit 10