题解 | #返回购买..产品的所有顾客的电子邮件(一)#
返回购买 prod_id 为 BR01 的产品的所有顾客的电子邮件(一)
https://www.nowcoder.com/practice/962b16554fbf4b99a87f4d68020c5bfb
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' ) ) 两层子嵌套