帮助sql查询

Question

表：

+-----+-----+----+ 
| Sym | Pos | Id | 
+-----+-----+----+ 
| a   | 0   | 0  | 
| b   | 1   | 0  | 
| c   | 2   | 0  | 
| a   | 0   | 1  | 
| d   | 1   | 1  | 
| b   | 0   | 2  | 
+-----+-----+----+ 

需要通过Id从此表行构建，然后按顺序Sym Pos。 在这种情况下，那将有：

+-----+-----+----+ 
| str | Pos | Id | 
+-----+-----+----+ 
| abc | 0   | 0  | 
| ad  | 0   | 1  | 
| b   | 0   | 2  | 
+-----+-----+----+

谢谢！

Answer 1

使用GROUP BY和MySQL特定的聚合函数GROUP_CONCAT：

SELECT GROUP_CONCAT(Sym ORDER BY Pos SEPARATOR '') AS str, Id
FROM yourtable
GROUP BY id

Answer 2

查看使用GROUP_CONCAT()