兩列組記錄

Question

我有名爲「invoices」的表。我想總結量和公司進行分組，並至今

+------------+------------------+-------------+-----------+ 
| 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  | 
+------------+------------------+-------------+-----------+ 

期望的結果是：

+------------+------------------+-------------+-----------+ 
| 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  | 
+------------+------------------+-------------+-----------+ 

我該怎麼辦呢？

Answer 1

你已經在英語規範在那裏，它只是需要轉換到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（取決於它的配置）脫身，而不做GROUP BY行，你可能看到您的旅行這樣SQLS通過MySQL的世界：

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

MySQL是由你..我個人倒總是建議把它放在明確，因爲一些其他的DB做一個「隱式插入組自動分組「，並堅持標準的SQL使你的SQL知識更便攜。您也可以「按組應始終隱」找到的強烈支持者的說法這，我承認，有其可取之:)

Answer 2

一起

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

對於分組由公司

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

對於按日期分組

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

Answer 3

使用下列內容：

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

更多有關GROUP BY條款和示例見here和here。