查询发现在MySQL

Question

重复的ID值的总和我有一个要求：需要

ID   Quantity 
1    5 
1    4 
1    2 
1    4 
2    1 
2    2 
2    3 
3    1 
3    3 
3    2 

输出：

ID   Quantity 
1    15 
2    6 
3    6 

我曾尝试下面的查询上的MySQL，但无法获得适当的结果。

SELECT 
a.id, sum(b.Quantity) 
FROM 
​table_name a 
INNER JOIN 
​table_name b 
ON a.id = b.id 
​ ​group by 
a.id, b.Quantity 

Answer 1

http://sqlfiddle.com/#!9/003625/1

SELECT id, SUM(quantity) 
FROM `table_name` 
GROUP BY id 

Answer 2

你不需要任何join。简单地尝试：

select id,sum(quantity) from table_name group by id 

Answer 3

使用GROUP BY子句sum()沿着像查询如下─

select ID, sum(Quantity) FROM table_name GROUP BY ID; 

Answer 4

刚刚从group by语句中删除b.Quantity。 SQL fiddle

SELECT 
a.id, sum(b.Quantity) 
FROM 
​table_name a 
INNER JOIN 
​table_name b 
ON a.id = b.id 
​ ​group by  
a.id