在mysql中选择行到列

Question

I have a table as shown below.

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

I would like to convert the above table as follows using select statement in Mysql.

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

I am using MySql 5.5 Please help.

Answer 1

Use a CASE expression if the count of Id column is fixed or known.

Query

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;

If the count of id column is unknown then you may need to use dynamic sql.

Query

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