每个不同的返回计数

Question

我有以下表格：

ORDER

OrderId
-------
Order1
Order2
Order3

CUSTOMERORDER

OrderId  CustomerId
-------  ----------
Order1   Cust1
Order1   Cust2
Order2   Cust3
Order3   Cust1

查询

select distinct count(*) as CustomersPerOrder
from CustomerOrder
group by CustomerOrder.OrderId
order by CustomersPerOrder

返回

CustomersPerOrder
-----------------
1
2

也就是说，有些订单有1个客户，有些有2个。我也想知道有多少订单有1个客户，有多少订单有2个：

CustomersPerOrder  OrdersCount
-----------------  -----------
1                  2
2                  1

也就是说，2个订单（OrdersCount）有1个客户（CustomersPerOrder），1个订单（OrdersCount）有2个客户（CustomersPerOrder）。

Answer 1

SELECT CustomersPerOrder, COUNT(*)
FROM
(
SELECT COUNT(*) as CustomersPerOrder
from CustomerOrder
group by CustomerOrder.OrderId
) sub
GROUP BY CustomersPerOrder

Answer 2

收起不同并计算CustomersPerOrder

的出现次数

with counter as (
 select count(customerid) as CustomersPerOrder
 from CustomerOrder
 group by CustomerOrder.OrderId
)
select CustomersPerOrder, COUNT(*) as OrdersCount 
from counter
group by CustomersPerOrder