Question

我有一个简单的表，您也可以在SQL Fiddle here中找到该表：

CREATE TABLE Orders (
    Customer TEXT,
    Order_Date DATE
);

INSERT INTO Orders
(Customer, Order_Date)
VALUES 
("Customer A", "2017-05-23"),
("Customer B", "2018-09-10"),
("Customer B", "2018-12-14"),
("Customer A", "2019-01-03"),
("Customer A", "2019-02-15"),
("Customer C", "2017-09-04"),
("Customer B", "2019-01-09"),
("Customer A", "2019-02-16"),
("Customer C", "2019-02-12"),
("Customer C", "2019-02-15"),
("Customer B", "2018-01-03");

您可以看到该表显示了来自不同客户的订单日期。
我使用下面的SQL来获得

的客户

a) placed an order in February 2019 and
b) did not place an order in the 12 month before and
c) placed an order before this 12 months period

请参阅此问题here的答案。

SELECT o.Customer
FROM ORDERS o
GROUP BY o.Customer
HAVING SUM( o.Order_Date >= '2019-02-01' AND o.Order_Date < '2019-03-01' ) > 0 AND
       SUM( o.Order_Date >= '2018-01-02' AND o.Order_Date < '2019-02-01' ) = 0 AND
       SUM( o.Order_Date < '2018-01-02' ) > 0 ;

到目前为止，所有这些都工作正常。

但是，现在我要实现的是，SQL既列出满足上述条件的客户，又列出counts客户在February 2019下的订单数量：

在上面的示例中，我期望得到以下结果：

Customer C     2

要实现此目的，我需要更改查询中的哪些内容？

Answer 1

只需将其添加到select：

SELECT o.Customer,
       SUM( o.Order_Date >= '2019-02-01' AND o.Order_Date < '2019-03-01' ) as num_feb_orders
FROM ORDERS o
GROUP BY o.Customer
HAVING SUM( o.Order_Date >= '2019-02-01' AND o.Order_Date < '2019-03-01' ) > 0 AND
       SUM( o.Order_Date >= '2018-01-02' AND o.Order_Date < '2019-02-01' ) = 0 AND
       SUM( o.Order_Date < '2018-01-02' ) > 0 ;

计算在特定时间段之前和之后存在的值

1 个答案: