Question

我有两个表，Staff和Cust_Order。我想在staff表中添加“First name”列同时仍然执行以下代码：

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

由于

Answer 1

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

使用不同，因为如果first_name不唯一，可能会出现重复结果。

Answer 2

将计数作为子查询

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

Answer 3

加入订单和员工表，然后分组将需要包含其他列

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
;

从一个表中选择计数，从另一个ORACLE中选择列

3 个答案: