Wordpress wp_query group by custom field

Question

I have to make a search form where i have to populate a select by the states of custom posts types. Some of them have the same state, then I would like to group-by to have a

Answer 1

I had to make a few improvements to Chirag Patels Code, to get it working:

postmeta . '.meta_value ';
    }
?>

 'observatoire',
    'post_status' => 'publish',
    'posts_per_page' => -1,
    'meta_key' => 'state'
)); 
?>


     
have_posts() ) : $states->the_post();
echo "".reset(get_post_custom_values('state')).""; 
endwhile;
?>