第六章 4-子查询vs连接|subqueries vs joins--Mosh my SQL

练习：

答案：

我的写法

select
distinct c.customer_id,
c.first_name,
c.last_name
from customers c
join orders o using (customer_id)
where o.order_id in
    (select oi.order_id
    from order_items oi
    where oi.product_id=3)

老师的写法

select
distinct customer_id,
first_name,
last_name
from customers c
join orders o using (customer_id)
join order_items oi using(order_id)
where oi.product_id=3