slightphp query sql leftjoin

slightphp query sql leftjoin

            $sql = "UPDATE mn_product_sell left join mn_product_base on mn_product_sell.product_id=mn_product_base.product_id set mn_product_sell.storage_data='{$s_data}' where mn_product_base.brand={$brand_id}";
            $res = M('mn_productsell')->query('mn_product_sell',$sql);