在没有枢轴和组concat的mysql中排成列

Question

I have a table like

ID    Student    Exam
----------------------  
1      Kavi      BE       
2      MGR       BA      
3      MGR1      BE  

I am writing this data in excel format.The problem is that i need the exam field to be a column-wise like,

BE      BA 
-------------
Kavi    NULL 
NULL    MGR
MGR1    NULL

This should be done only with the query,because i can't modify excel class to make it to print column-wise data.

I have used group concat,but i need the exam details to be of a separate column and not in same column.I shouldnot use pivot since it is not supported by few versions of mysql. Pls Help.

Note: This table may have as many as records,so pls provide solutions that can work dynamically.

Answer 1

MySQL doesn't have a PIVOT function so you will need to use an aggregate function with a CASE expression to get the result:

select
  max(case when exam = 'BE' then student end) BE,
  max(case when exam = 'BA' then student end) BA
from yourtable
group by id;

See SQL Fiddle with Demo .

If you are going to have an unknown number of exam values then you will need to look at using a prepared statement with dynamic sql. The code will be similar to:

SET @sql = NULL;
SELECT
  GROUP_CONCAT(DISTINCT
    CONCAT(
      'max(case when exam = ''',
      exam,
      ''' then student end) AS `',
      exam, '`'
    )
  ) INTO @sql
from yourtable;

SET @sql 
    = CONCAT('SELECT ', @sql, ' 
              from yourtable
              group by id;');

PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

See SQL Fiddle with demo . Both versions give the result:

|     BE |     BA |
|   Kavi | (null) |
| (null) |    MGR |
|   MGR1 | (null) |