SQL 查询用户每月的最大金额

Question

我想打印最大金额的用户每月的最大金额。我的 table 结构是

+--------------+-------------+------+-----+---------+-------+
| Field        | Type        | Null | Key | Default | Extra |
+--------------+-------------+------+-----+---------+-------+
| customername | varchar(20) | YES  |     | NULL    |       |
| processed_at | date        | YES  |     | NULL    |       |
| amount       | int(11)     | YES  |     | NULL    |       |
+--------------+-------------+------+-----+---------+-------+

和打印月最大总和的查询是

SELECT MAX(A.AMT), A.month
FROM ( SELECT customername,SUM(amount) AS AMT, EXTRACT( month from processed_at) as month
FROM payments
GROUP BY customername,month) AS A
GROUP BY  2;

这是给出的结果

| MAX(A.AMT) | month |
+------------+-------+
|       1900 |     4 |
|       2400 |     3 |

有没有办法将客户名也映射到最大金额？

Answer 1

如果你是运行 MySQL 8.0，你可以使用 window 功能：

SELECT *
FROM (
    SELECT 
        customername,
        SUM(amount) amt, 
        DATE_FORMAT(processed_at, '%Y-%m-01') yr_month,
        RANK() OVER(PARTITION BY DATE_FORMAT(processed_at, '%Y-%m-01') ORDER BY SUM(amount) DESC) rn
    FROM payments
    GROUP BY customername, yr_month
) t
WHERE rn = 1

请注意，这在 GROUP BY 子句中包括月份和年份，以防您的数据分布超过 12 个月。

在早期版本中，一种选择是使用 HAVING 子句和相关聚合查询进行过滤：

SELECT 
    customername,
    SUM(amount) amt, 
    DATE_FORMAT(processed_at, '%Y-%m-01') yr_month
FROM payments p
GROUP BY customername, yr_month
HAVING COUNT(*) = (
    SELECT SUM(p1.amount)
    FROM payments p
    WHERE DATE_FORMAT(p1.processed_at, '%Y-%m-01') = yr_month
    GROUP BY p1.customername
    ORDER BY SUM(p1.amount) DESC
    LIMIT 1
)

SQL 查询用户每月的最大金额

SQL query for finding maximum amount month wise with the user

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