试图编写最受欢迎的产品(意味着拥有最独特客户的产品)的查询超级困难.而不使用view



with mostCustomers (pid, cnt) as
(
select 
li.PID, count(distinct o.CID) customers
from LineItem li
inner join order o on o.OID = li.OID
group by li.PID
),
maxCustomers (customers) as (select max(customers) from mostCustomers)
select p.ProductName
from mostCustomers mc
inner join maxCustomers mx on mx customers = mc.customers
inner join product p on p.PID = mc.PID;

您应该给出示例数据和预期输出。此外，你应该用你正在使用的后端标记你的问题。以上查询适用于大多数情况，但不能适用于所有情况。下次请这样做。