单次交易中每位客户每年的总销售额答案

【问题标题】：agregate sales totals per years per customer in one transaction单次交易中每位客户每年的总销售额
【发布时间】：2022-01-01 00:19:37
【问题描述】：

我有一个正常的周转表，有 3 列“客户”、“年份”、“金额” （例如）

customer	year	amount
anton	2020	$5
paul	2019	$12
anton	2021	$5
paul	2019	$10
felicia	2021	$5
anton	2019	$12
felipe	2019	$12

我有以下 mysql 查询

SELECT `customer` , SUM(`amount`) as summ FROM `customer`.`accountsales` WHERE `amount`> 0 GROUP BY `customer` ORDER BY summ DESC ;

这个交易给了我一个很好的帕累托表，每个客户的销售额按降序排列

name	sales all years
customer1	sum of all transactions of customer1
customer2	sum of all transactions of customer2
customer3	sum of all transactions of customer3

到目前为止一切顺利，我想更进一步，我想创建下表

Name	Sales all years	Sales 2021	Sales2020	Sales2019
customer1	sum1	sum2021 from customer1	sum2020 from customer1	sum2019 from customer1
customer2	sum2	sum2021 from customer2	sum2020 from customer2	sum2019 from customer2
customer3	sum3	sum2021 from customer3	sum2020 from customer3	sum2019 from customer3

但我只想在一个事务中完成，因为初始表非常大。

谁能给个提示？

附言请随意编辑标题，因为我今天不太受启发

【问题讨论】：

到目前为止您尝试过什么？你被困在哪里了？

标签： mysql

【解决方案1】：

你可以尝试使用条件聚合函数

查询 1：

SELECT `customer` , 
       SUM(`amount`) 'Sales all years',
        SUM(CASE WHEN year = 2021 THEN `amount` ELSE 0 END)  Sales2021,
        SUM(CASE WHEN year = 2020 THEN `amount` ELSE 0 END)  Sales2020,
        SUM(CASE WHEN year = 2019 THEN `amount` ELSE 0 END)  Sales2019
FROM accountsales
GROUP BY `customer`

Results：

| customer | Sales all years | Sales2021 | Sales2020 | Sales2019 |
|----------|-----------------|-----------|-----------|-----------|
|    anton |              22 |         5 |         5 |        12 |
|  felicia |               5 |         5 |         0 |         0 |
|   felipe |              12 |         0 |         0 |        12 |
|     paul |              22 |         0 |         0 |        22 |

【讨论】：