select一次查询的结果在另一个表中发生

Question

假设我有两张桌子:

USERS:
User_Id
Hansen
Nilsen
Jensen
Bob

和

ORDERS:
O_Id    OrderDate   OrderPrice  Customer
1       2008/11/12  1000        Hansen
2       2008/10/23  1600        Nilsen
3       2008/09/02  700         Hansen
4       2008/09/03  300         Hansen
5       2008/08/30  2000        Jensen
6       2008/10/04  100         Nilsen

我想做一个查询来显示客户订购的次数,所以它看起来像:

Customer    Orders
Hansen      3
Nilsen      2
Jensen      1
Bob         0

我知道我必须使用COUNT函数,但我不知道如何完成这个查询...

Answer 1

SELECT     Customer, COUNT(*) AS Orders 
FROM         ORDERS  RIGHT OUTER JOIN
                      USERS ON USERS.User_Id = ORDERS.Customer
GROUP BY USERS.User_Id
ORDER BY COUNT(*) DESC