modify default query for custom_post in admin (list, columns))

Hi,

I’m trieing to extend the deafault query with a left join on an additional table.

function accommodation_join( $join ) {
	global $wp_query, $wpdb;
	if( $_GET['post_type']  == 'accommodation' ) {
    	$join .= " LEFT JOIN accommodation ON " . $wpdb->posts . ".ID = 'accommodation.__idPost' ";
	}
	return $join;
}
add_filter('posts_join', 'accommodation_join' );

This seems to work but this returns:
SELECT SQL_CALC_FOUND_ROWS wp_posts.* FROM wp_posts LEFT JOIN accommodation ON wp_posts.ID = 'accommodation.__idPost' WHERE 1=1 AND wp_posts.post_type = 'accommodation' AND (wp_posts.post_status = 'publish' OR wp_posts.post_status = 'future' OR wp_posts.post_status = 'draft' OR wp_posts.post_status = 'pending' OR wp_posts.post_status = 'private') ORDER BY wp_posts.post_date DESC LIMIT 0, 20

It askes for the fields in wp_posts only wp_posts.* but I need information from the accommodation table also.

Is there any way to achieve this?

I hope somebody can help!