题解 | #返回每个顾客不同订单的总金额#

SELECT 
    o.cust_id cust_id,
    tb.total_ordered total_ordered
FROM (
    SELECT
        order_num,
        SUM(item_price * quantity) total_ordered
    FROM
        OrderItems
    GROUP BY
        order_num
    ) tb,
    Orders o
WHERE
    tb.order_num = o.order_num
ORDER BY
    total_ordered DESC;