issues with mysql GROUP_CONCAT and INSERT into another table

I have a MySQL GROUP_CONCAT .... INSERT issue This code works:

    SELECT group_concat(tabel2.img_name separator ',') 
    FROM tabel2 
    GROUP BY tabel2.produit_id

I need to insert the result into another table and I'm stuck.

This (or any combination I could think of) doesn't work

    INSERT INTO tabel1.imgname
    SELECT group_concat(tabel2.img_name separator ',') 
    FROM tabel2 
    GROUP BY tabel2.produit_id 
    WHERE tabel1.product_id = tabel2.produit_id

What am I doing wrong?

CREATE TABLE IF NOT EXISTS `tabel1` (
  `product_id` int(11) NOT NULL AUTO_INCREMENT,
  `rubrique_id` int(11) NOT NULL,
  `marque_id` int(11) NOT NULL,
  `subfamily_id` int(11) NOT NULL,
  `product_name` varchar(150) NOT NULL,
  `imgname` varchar(255) DEFAULT NULL,
  `product_description1` text NOT NULL,
  `product_description2` text NOT NULL,
  `product_order` int(11) NOT NULL,
  `product_page` int(11) NOT NULL,
  `price_min` float NOT NULL,
  PRIMARY KEY (`product_id`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=0;


    INSERT INTO `tabel1` (`product_id`, `rubrique_id`, `marque_id`, `subfamily_id`, `product_name`, `imgname`, `product_description1`, `product_description2`, `product_order`, `product_page`, `price_min`) 
VALUES
(33, 15, 23, 40, 'product 1', NULL, '', '', 0, 0, 0),
(34, 13, 13, 13, 'product 2', NULL, '', '', 0, 0, 0),
(35, 14, 14, 14, 'product 3', NULL, '', '', 0, 0, 0);



CREATE TABLE IF NOT EXISTS `tabel2` (
  `img_id` int(11) NOT NULL AUTO_INCREMENT,
  `img_name` text NOT NULL,
  `article_id` int(11) DEFAULT NULL,
  `produit_id` int(11) DEFAULT NULL,
  `product_select` tinyint(1) DEFAULT NULL,
  PRIMARY KEY (`img_id`)
) ENGINE=MyISAM  DEFAULT CHARSET=latin1 AUTO_INCREMENT=4018 ;

INSERT INTO `tabel2` (`img_id`, `img_name`, `article_id`, `produit_id`, `product_select`) 
VALUES
(4013, 'acoacki086050.jpg', 13342, 33, NULL),
(4014, '32252il6jh2dqex.jpg', NULL, 34, NULL),
(4015, '33265ulrzmgr18w.jpg', NULL, 34, NULL),
(4016, '40334zcfk0c4n67.jpg', NULL, 35, NULL),
(4017, '40473frd4900u82.jpg', NULL, 35, NULL);

So for say tabel1.product_id = 34 I need to have tabel1.imgname = 32252il6jh2dqex.jpg,33265ulrzmgr18w.jpg

Solution

What you describe is UPDATE. not INSERT:

UPDATE
    tabel1 AS t1
  JOIN
    ( SELECT produit_id
           , GROUP_CONCAT(img_name SEPARATOR ',') AS grp_img_name
      FROM tabel2 
      GROUP BY produit_id
    ) AS t2
        ON t2.produit_id = t1.product_id
SET
    t1.imgname = t2.grp_img_name ;

Random rants:

Why, why, why do you have these table1, tabel1, tabel2, tableX names? Names of any object (of tables, columns, indexes, constraints, databases) should reflect usage.
table1 says nothing.
tabel1 says nothing except that you don't spell-check your names.

It's good practice that columns used in Foreign Key constraints (and as a result for joining), have identical names (if possible). Not imgname in one table and img_name in another. Not produit_id in one and product_id in the other. It helps you, the next programmer and the guys who try to help you over SO, to not make mistakes writing ON t2.produit_id = t1.produit_id. It can also help, if you like the USING (product_id) syntax instead of the ON syntax for joins.

(update)
It seems that the different names are because the tables come from different sources/databases and it was not your choice. I would suggest you alter them to have uniform/sensible names, if you have a lot of work to do with them. If it's a one-time job, just to transfer/transform some data, don't bother.