题解 | #返回购买某产品的所有顾客的电子邮件-子查询#

# 查询购买prod_id为BR01的产品的所有顾客号
select cust_id
from OrderItems oi
join Orders o
on oi.order_num=o.order_num
where prod_id='BR01'
# 查询购买prod_id为BR01的产品的所有顾客的电子邮件
select cust_email
from Customers
where cust_id in (
    select cust_id
    from OrderItems oi
    join Orders o
    on oi.order_num=o.order_num
    where prod_id='BR01'
);