题解 | #返回购买 prod_id 为 BR01 的产品的所有顾客的电子邮件（一）#

SELECT 
    cust_email
FROM
    Customers
WHERE
    cust_id IN (
        SELECT 
            cust_id
        FROM
            Orders
        WHERE
            order_num IN (
                SELECT
                    order_num
                FROM
                    OrderItems
                WHERE
                    prod_id = 'BR01'
            )
    );