MySQL SUM在使用GROUP BY时不起作用 [英] MySQL SUM when using GROUP BY not working

问题描述

假设我们有这张表：

 符号|大小
 A | 12 
 B | 5 
 A | 3 
 A | 6 
 B | 8 
  

我们希望看到如下图：

 符号|大小
 A | 21 
 B | 
 
 
 
 
 $ p> 从符号表中选择Symbol，sum（Size）按符号顺序按符号ASC 
  

但是我们得到这个：



 符号|大小
 A | 12 
 B | 5 
  

我做错了什么？！


Select 命令的某个地方发现了Un-SUMable表，而不是左连接有一个简单的连接。虽然我仍然不明白为什么这会弄乱计算，我改变了这一点，现在它作品......对不起，我无法上传整件事......

Let's say we have this table:

Symbol | Size
A      | 12
B      | 5
A      | 3
A      | 6
B      | 8

And we want a view like this:

Symbol | Size
A      | 21
B      | 13

So we use this:

Select Symbol, sum(Size) from table group by Symbol order by Symbol ASC

But instead we get this:

Symbol | Size
A      | 12
B      | 5

What am I doing wrong?!

解决方案

I found out that somewhere in the Select commands that leaded to the Un-SUMable table instead of a left join there was a simple join.Although I still don't get why that should mess up the calculation, I changed that and now it works... I'm sorry I couldn't upload the whole thing...

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