题解 | #返回每个顾客不同订单的总金额#

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