高级MySQL查询，组1列

Question

如果这是可能

我有在碱这样的：

AAA 1 
AAA 2 
BBB 1 
BBB 2 
BBB 3 

和结果必须是这样

AAA 1 2 
BBB 1 2 3 

或

AAA 1,2 
BBB 1,2,3 

tnx

Answer 1

使用GROUP_CONCAT。

查询

select column1, 
group_concat(column2 separator ',') as column2 
from tableName 
group by column1; 

结果

+---------+---------+ 
| column1 | column2 | 
+---------|---------+ 
| AAA  | 1,2  | 
| BBB  | 1,2,3 | 
+---------+---------+ 

SQL Fiddle

如果你想与空间()而不是逗号(,)分离，
ŧ母鸡在group_concat中指定separator ' '。

然后查询将会像下面：

select column1, 
group_concat(column2 separator ' ') as column2 
from tableName 
group by column1; 

结果

+---------+---------+ 
| column1 | column2 | 
+---------|---------+ 
| AAA  | 1 2  | 
| BBB  | 1 2 3 | 
+---------+---------+ 

Read more about group_concat here

UPDATE

如果您需要单独列中的每个column2值，
那么您可能需要执行动态SQL查询。

查询

set @query = null; 
select 
group_concat(distinct 
    concat(
     'max(case when column2 = ''', 
     column2, ''' then column2 end) as Value_',column2 
    ) 
) into @query 
from tableName ; 

set @query = concat('select column1, ', @query, ' from tableName 
        group by column1 
'); 

prepare stmt from @query; 
execute stmt; 
deallocate prepare stmt; 

结果

+---------+---------+---------+---------+ 
| column1 | Value_1 | Value_2 | Value_3 | 
+---------+---------+---------+---------+ 
| AAA  | 1  | 2  | (null) | 
| BBB  | 1  | 2  | 3  | 
+---------+---------+---------+---------+ 

SQL Fiddle