$sql=$wpdb->prepare("SELECT meta_key , (SELECT id from ".$wpdb->users." WHERE user_login=substring(meta_key,2)) as id ,(SELECT display_name from ".$wpdb->users." WHERE user_login=substring(meta_key,2)) as display_name FROM ".$wpdb->postmeta." where meta_value='like' and post_id=%d",$post_id);