题解 | #返回购买 prod_id 为 BR01 的产品的所有顾客的电子邮件（二）#

select cust_email
from OrderItems as os
left join Orders o
on os.order_num = o.order_num
left join Customers c
on o.cust_id = c.cust_id
where prod_id = 'BR01'

SELECT 
    c.cust_email cust_email
FROM
    OrderItems oi INNER JOIN Orders o ON
    (oi.prod_id = 'BR01') AND
    (oi.order_num = o.order_num) INNER JOIN Customers c ON
    o.cust_id = c.cust_id;