显示所有在夏季没有买东西的客户

Question

我有两个表“ OEHR_Orders”和“ OEHR_Customers”。

客户和订单都有链接的Customer_ID。 我现在想显示所有在7月或8月没有购买任何商品的客户。 这是我的查询：

SELECT DISTINCT C.CUST_LAST_NAME ||'.'||SUBSTR(C.CUST_First_Name,1,1) AS "Name"
FROM OEHR_Customers C INNER JOIN OEHR_ORDERS O
ON C.Customer_ID = O.Customer_ID
WHERE EXTRACT(MONTH FROM O.Order_Date) NOT BETWEEN '7' and '8'

不幸的是，这个查询没有给我想要的结果。

有什么想法吗？

Answer 1

SELECT DISTINCT CUST_LAST_NAME ||'.'||SUBSTR(CUST_First_Name,1,1) AS "Name"
FROM OEHR_Customers
WHERE Customer_Id not in (Select Customer_ID from OEHR_ORDERS
            WHERE EXTRACT(MONTH FROM Order_Date) NOT BETWEEN '7' and '8')

Answer 2

我倾向于使用GROUP BY和HAVING做到这一点：

SELECT C.CUST_LAST_NAME || '.' || SUBSTR(C.CUST_First_Name, 1, 1) AS "Name"
FROM OEHR_Customers C INNER JOIN
     OEHR_ORDERS O
     ON C.Customer_ID = O.Customer_ID
GROUP BY C.CUST_LAST_NAME || '.' || SUBSTR(C.CUST_First_Name, 1, 1)
HAVING SUM(CASE WHEN EXTRACT(MONTH FROM O.Order_Date) BETWEEN 7 and 8
                THEN 1 ELSE 0 END) = 0;

HAVING子句计算第7个月和第8个月出现的次数。 然后，它将筛选出在这几个月内有购买交易的客户。

您所查询的版本只会吸引在这几个月内没有购买的客户。