两列组记录

Question

我有名为“invoices”的表。我想总结量和公司进行分组，并至今

+------------+------------------+-------------+-----------+ 
| company_id | company   | date  | amount | 
+------------+--------------------------------+-----------+ 
| 1  | chevrolet  | 2017-11-18 | 100  | 
| 1  | chevrolet  | 2017-11-18 | -70  | 
| 1  | chevrolet  | 2017-11-25 | 50  | 
| 2  | mercedes   | 2017-04-01 | 30  | 
| 2  | mercedes   | 2017-04-01 | -30  | 
| 2  | mercedes   | 2017-09-01 | 50  | 
| 3  | toyota   | 2017-05-12 | 60  | 
+------------+------------------+-------------+-----------+ 

期望的结果是：

+------------+------------------+-------------+-----------+ 
| company_id | model_name  | date  | amount | 
+------------+--------------------------------+-----------+ 
| 1  | chevrolet  | 2017-11-18 | 30  | 
| 1  | chevrolet  | 2017-11-25 | 50  | 
| 2  | mercedes   | 2017-04-01 | 0  | 
| 2  | mercedes   | 2017-09-01 | 50  | 
| 3  | toyota   | 2017-05-12 | 60  | 
+------------+------------------+-------------+-----------+ 

我该怎么办呢？

Answer 1

你已经在英语规范在那里，它只是需要转换到SQL：

select company_id, model_name, date, sum(amount) as amount 
from invoices 
group by company_id, model_name, date 

在MySQL中，你可以（取决于它的配置）脱身，而不做GROUP BY行，你可能看到您的旅行这样SQLS通过MySQL的世界：

select company_id, model_name, date, sum(amount) as amount 
from invoices 

MySQL是由你..我个人倒总是建议把它放在明确，因为一些其他的DB做一个“隐式插入组自动分组“，并坚持标准的SQL使你的SQL知识更便携。您也可以“按组应始终隐”找到的强烈支持者的说法这，我承认，有其可取之:)

Answer 2

一起

SELECT 
SUM (amount) 
FROM <table-name> 
GROUP BY company, date; 

对于分组由公司

SELECT 
SUM (amount) 
FROM <table-name> 
GROUP BY company; 

对于按日期分组

SELECT 
SUM (amount) 
FROM <table-name> 
GROUP BY date; 

Answer 3

使用下列内容：

SELECT company_id, model_name, date , SUM(amount) AS amount 
      FROM invoices GROUP BY company, date; 

更多有关GROUP BY条款和示例见here和here。