$args = array( 'post_type' => 'product', 'meta_query' => array( 'relation' => 'OR', array( // Simple products type 'key' => '_sale_price', 'value' => 0, 'compare' => '>', 'type' => 'numeric' ), array( // Variable products type 'key' => '_min_variation_sale_price', 'value' => 0, 'compare' => '>', 'type' => 'numeric' ) ) ); query_posts( $args );