MySQL select specific row values as column names

Question

Here is my basic participants table (displayed as associative array):

[id] => 1
[campaign_id] => 41
[firstname] => Jeff
[lastname] =>         


        

Answer 1

SELECT  a.ID,
        a.Campaign_ID,
        a.FirstName,
        a.LastName,
        MAX(CASE WHEN b.data = 'qwerty1' THEN b.Name END) qwerty1,
        MAX(CASE WHEN b.data = 'qwerty2' THEN b.Name END) qwerty2,
        MAX(CASE WHEN b.data = 'qwerty3' THEN b.Name END) qwerty3
FROM    Participants a
        INNER JOIN Participants_Custom b
            ON a.ID = b.Participant_ID
GROUP   BY  a.ID,
            a.Campaign_ID,
            a.FirstName,
            a.LastName

• SQLFiddle Demo

UPDATE 1

Since the values of data are unknown, a dynamic sql is much preferred.

SET @sql = NULL;
SELECT
  GROUP_CONCAT(DISTINCT
    CONCAT(
      'MAX(CASE WHEN b.data = ''',
      data,
      ''' THEN b.Name ELSE NULL END) AS ',
      CONCAT('`',data, '`')
    )
  ) INTO @sql
FROM Participants_Custom;

SET @sql = CONCAT('SELECT  a.ID,
                           a.Campaign_ID,
                           a.FirstName,
                           a.LastName,', @sql, 
                  'FROM     Participants a
                            INNER JOIN Participants_Custom b
                                ON a.ID = b.Participant_ID
                    GROUP   BY  a.ID,
                                a.Campaign_ID,
                                a.FirstName,
                                a.LastName');

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

• SQLFiddle Demo