查詢發現在MySQL

Question

重複的ID值的總和我有一個要求：需要

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

輸出：

ID   Quantity 
1    15 
2    6 
3    6 

我曾嘗試下面的查詢上的MySQL，但無法獲得適當的結果。

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。簡單地嘗試：

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

Answer 3

使用GROUP BY子句sum()沿着像查詢如下─

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

Answer 4

剛剛從group by語句中刪除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