This will add new search field in custom post type default search field
/* add search option by job id in wp admin */ add_filter('posts_where', 'posts_where'); function posts_where($where) { global $wpdb; $curent_posttype = $_GET['post_type']; if ($curent_posttype == 'jobs') { $where .= " OR ID IN (SELECT post_id FROM bh_job_id_assignment WHERE id='{$_GET['s']}' )"; //"bh_job_id_assignment" custom table } return $where; }