mysql - 根据条件过滤sql查询

Question

我有一个表应该是这样的:

CREATE TABLE orders
(
    order_number int PRIMARY KEY,
    client varchar(20),
    revenue int,
    fixed_transport_cost int,
    income int,
    order_date date
)

我期望的是这样的:

Select clients whose first order was placed in 2017 and calculate how much income was genereted in 2018 (total) per each of them.

我尝试过的是:

 SELECT 
     clients, SUM(income) 
 FROM
     orders 
 HAVING 
     YEAR(order_date) = '2018' 
     AND income = ANY (SELECT income FROM orders 
                       WHERE YEAR(order_date) = '2017') 
 GROUP BY
     income;

但看起来查询不正确。我的问题是如何检查是否有人在 2017 年订购过？

Answer 1

1. 首先，HAVING 子句应放在 GROUP BY 子句之后。
2. 其次，您应该检查 2017 年的第一笔订单，而不是 2017 年的任何订单。这就是您所要求的。事实上，HAVING 在这里不是必需的。
3. 您需要按客户分组，因为您正在查找每个客户的收入总和(如果我理解得很好的话)。

您可以尝试以下查询:

 SELECT 
     client, SUM(income) 
 FROM
     orders 
 WHERE
     YEAR(order_date) = '2018' 
     AND client IN (
          SELECT client 
          FROM orders 
          GROUP BY client 
          HAVING MIN(YEAR(order_date)) = '2017')
 GROUP BY
     client;

或者

 SELECT 
     o1.client, SUM(o1.income) 
 FROM
     orders o1
 WHERE
     YEAR(o1.order_date) = '2018' 
     AND '2017' = (
          SELECT MIN(YEAR(o2.order_date))
          FROM orders o2
          WHERE o2.client = o1.client)
 GROUP BY
     o1.client;

如果您希望我们尝试查询并为您提供演示，请提供数据示例。