题解 | #确定最佳顾客的另一种方式（二）#

inner join  同 join
where后面不能接聚集函数，如sum（），having才可以
同一字段涉及不同表，选择的时候要记得加上具体表名，如cust_name

方法一：join on
select c.cust_name,
sum(oi.item_price*oi.quantity) total_price
from Orders o
inner join OrderItems oi
on o.order_num=oi.order_num
inner join Customers  c
on o.cust_id=c.cust_id
group by  c.cust_name
having total_price >= 1000
order by total_price

方法二：join using
select c.cust_name,
sum(oi.item_price*oi.quantity) total_price
from Orders o
inner join OrderItems oi
using(order_num)
inner join Customers  c
using(cust_id)
group by  c.cust_name
having total_price >= 1000
order by total_price