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

You can try below code:

postmeta . '.meta_key = "state"';
    }
?>

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


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

Query Look like:

SELECT wp_posts.*
FROM wp_posts INNER JOIN wp_postmeta 
  ON (wp_posts.ID = wp_postmeta.post_id)
WHERE wp_posts.post_type = 'observatoire'
  AND (wp_posts.post_status = 'publish')
  AND (wp_postmeta.meta_key = 'state' )
GROUP BY wp_postmeta.meta_key = "state"
ORDER BY wp_posts.post_date DESC