MYSQL group by 当大于 X

Posted 2023-02-24

【中文标题】MYSQL group by 当大于 X

【英文标题】：MYSQL group by when greater than X

【发布时间】：2020-04-05 19:19:09

【问题描述】：

让我解释一下我的问题。 在 mysql 中，我有一个这样的订单表（简化）：

+------------+-------+
| customerID | price | 
+------------+-------+
| 10         | 10    |
| 20         | 10    |
| 20         | 10    |
| 30         | 10    |
| 30         | 10    |
| 30         | 10    |
| 120        | 10    |
| 120        | 10    |
| 130        | 10    |
| 130        | 10    |
| 130        | 10    |
| 130        | 10    |
+------------+-------+

我想要总价的订单数量的客户数量。

+-----------------------------+--------------------+-------------+  
| number_of_order_by_customer | number_of_customer | total_price |  
+-----------------------------+--------------------+-------------+  
| 1                           | 1                  | 10          |  
| 2                           | 2                  | 40          |  
| 3 and more                  | 2                  | 70          |  
+-----------------------------+--------------------+-------------+  

我们可以像这样阅读这张表： - 1 位客户以 10 欧元订购了 1 次（客户 10） - 2 位客户订购了 2 次，共计 40 欧元（客户 20 和客户 120） - 2 位客户订购 3 次或更多，总计 70 欧元（客户 30（3 次）和客户 130（4 次））

我的问题是“3 和更多” 有了这个请求，我可以有 1、2、3、4 次，但我不知道如何分组 3 和 4 次

SELECT 
    number_of_order_by_customer, COUNT(number_of_order_by_customer) AS number_of_customer, SUM(price) AS total_price 
FROM
(
    SELECT
        COUNT(o.customerID ) AS number_of_order_by_customer, sum(o.price ) AS price
    FROM 
        order o
    GROUP BY o.customerID 
) AS tmp

GROUP BY number_of_order_by_customer
;

我明白了：

+-----------------------------+--------------------+-------------+  
| number_of_order_by_customer | number_of_customer | total_price |  
+-----------------------------+--------------------+-------------+  
| 1                           | 1                  | 10          |  
| 2                           | 2                  | 40          |  
| 3                           | 1                  | 30          |  
| 4                           | 1                  | 40          |
+-----------------------------+--------------------+-------------+  

有谁知道如何在同一个请求中获得“3 个或更多”？

【参考方案1】：

表达式时的用例-

SELECT 
    case when number_of_order_by_customer>=3 then '3 or More' else cast(number_of_order_by_customer as varchar(10)) end as number_of_order_by_customer, COUNT(nb) AS number_of_customer, SUM(price) AS total_price 
FROM
(
    SELECT
        COUNT(o.customerID ) AS number_of_order_by_customer, sum(o.price ) AS price
    FROM 
        order o
    GROUP BY o.customerID 
) AS tmp

GROUP BY case when number_of_order_by_customer>=3 then '3 or More' else cast(number_of_order_by_customer as varchar(10)) end

【讨论】：

超级，但转换为 varchar 不起作用。将其转换为 char ***.com/a/15368838/12524340