Get not related Posts to Posts objects

p2p-not-related.php

<?php

	/**
	 * Get all CPT XX not related to an other CPT YY
	 *
	 * @return array
	 * @author Alexandre Sadowski
	 */
	function get_not_related() {
		/**
		 * @var $wpdb wpdb
		 */
		global $wpdb;
		return $wpdb->get_col(
			$wpdb->prepare( "
				SELECT p.ID FROM
				$wpdb->posts p
					LEFT JOIN $wpdb->p2p pp
					ON p.ID = pp.p2p_from
				WHERE pp.p2p_from IS NULL
				AND p.post_type = %s,
				AND p.post_status = 'publish',
				CPT-XX) );
	}