Question

我有一张桌子如下所示。

**id | location**
1  | East Flow
2  | East Level
3  | East Pressure

我想在Mysql中使用select语句将上面的表转换如下。

1          | 2           | 3  
East Flow  | East Level  | East Pressure

我正在使用MySql 5.5 请帮忙。

Answer 1

如果Id列的计数已修复或已知，请使用CASE表达式。

<强>查询

select max(case when id = 1 then location end) as `1`,
max(case when id = 2 then location end) as `2`,
max(case when id = 3 then location end) as `3`
from your_table;

如果id列的计数未知，则可能需要使用动态sql。

<强>查询

select
group_concat(distinct
    concat(
      'max(case when id = ',
      id,' then location end) as `', id,'`'
    )
  ) into @sql
from your_table;

set @sql = concat('select ', @sql, ' from your_table');

prepare stmt from @sql;
execute stmt;
deallocate prepare stmt;

SQL Fiddle

在mysql中选择行到列

1 个答案: