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 DISTINCT C.cust_email
FROM Customers C
JOIN Orders O ON C.cust_id = O.cust_id
JOIN OrderItems OI ON O.order_num = OI.order_num
WHERE OI.prod_id = 'BR01';