从一个表中选择计数，从另一个列中选择计数ORACLE

Question

我有两个表，Staff和Cust_Order。我想从工作人员的表 添加列“名字”，同时仍然执行下面的代码：

Select Staff_No Count(*) AS "Number Of Orders" 
From Cust_Order 
Group by Staff_No; 

感谢

Answer 1

加入订单和员工表，然后按需要包括其他列（S）

SELECT 
     co.Staff_No 
    , s.First_name 
    , COUNT(*) AS "Number Of Orders" 
FROM Cust_Order co 
INNER JOIN Staff s on co.Staff_No = s.Staff_No 
GROUP BY 
     co.Staff_No 
    , s.First_name 
; 

Answer 2

SELECT DISTINCT 
    STAFF_NO, 
    FIRST_NAME, 
    COUNT (*) OVER (PARTITION BY STAFF_NO) AS "Number Of Orders" 
FROM CUST_ORDER; 

使用不同的，因为可能有重复结果的情况下，FIRST_NAME不独特。

Answer 3

得到计数作为一个子查询

Select First_Name, 
(Select Count(*) From Cust_Order o 
     Where o.STAFF_NO = Cust_Order.STAFF_NO) "Number Of Orders" 
From Cust_Order