Mysql multiple select with multiple different where conditions in the same query

Question

I have the following table :

+--------------------+-----------+--------------------+
| Product            | website   | is_master          |
+--------------------+-----------+--------------------+
| product A          |       X   | 1                  |
| product A          |       Y   | 0                  |
| product A          |       Z   | 0                  |
| product A          |       C   | 0                  |
| product B          |       D   | 1                  |
| product C          |       E   | 1                  |
+--------------------+-----------+--------------------+

I am trying to make a mysql query to get a table a as the following one :

+--------------------+------------------+--------------------+
| Product            | master_website   | additional_sites   |
+--------------------+------------------+--------------------+
| product A          |       X          | y,z,c              |
| product B          |       D          | null               |
| product C          |       E          | null               |
+--------------------+------------------+--------------------+

I have tried with a subselect query but I failed in both cases.

select 
Product, 
    (select Product 
     FROM `table1` 
     LEFT JOIN 
     table2 on table1.id = table2.fk_table1 
     WHERE is_master = 1) is_master, 

    (select group_concat(Product) 
     FROM `table1` 
     LEFT JOIN 
     table2 on table1.id = table2.fk_table1 
     WHERE is_master = 0) additional 

     FROM `table1` 
     LEFT JOIN 
     table2 on table1.id = table2.fk_table1 

WHERE 1 
group by 
Product 

The problem is that the subselect returns more than one row.

Answer 1

SQL Fiddle

SELECT t1.Product,
          t1.website AS master_website, 
          GROUP_CONCAT(t2.website ORDER BY t2.website) AS additional_sites   
     FROM MyTable t1
LEFT JOIN MyTable t2 
       ON t1.Prduct = t2.Prduct AND 
          t2.is_master = 0
    WHERE t1.is_master = 1
 GROUP BY t1.Product