MySQL pivot table query with dynamic columns

Question

I\'m using the following tables for storing product data:

mysql> SELECT * FROM product;
+---------------+---------------+--------+
| id | name     | descr         


        

Answer 1

I have a slightly different way of doing this than the accepted answer. This way you can avoid using GROUP_CONCAT which has a limit of 1024 characters and will not work if you have a lot of fields.

SET @sql = '';
SELECT
    @sql := CONCAT(@sql,if(@sql='','',', '),temp.output)
FROM
(
    SELECT
      DISTINCT
        CONCAT(
         'MAX(IF(pa.fieldname = ''',
          fieldname,
          ''', pa.fieldvalue, NULL)) AS ',
          fieldname
        ) as output
    FROM
        product_additional
) as temp;

SET @sql = CONCAT('SELECT p.id
                    , p.name
                    , p.description, ', @sql, ' 
                   FROM product p
                   LEFT JOIN product_additional AS pa 
                    ON p.id = pa.id
                   GROUP BY p.id');

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