$sql ="update lzh_cds_items set ci_fetch_num = ci_fetch_num+(-20)";
这么写对吗
……加负值，不就是减吗？？？
$sql ="update lzh_cds_items set ci_fetch_num = ci_fetch_num-20";
![[Web front-end] Démarrage rapide de Node.js](https://img.php.cn/upload/course/000/000/067/662b5d34ba7c0227.png)
……加负值，不就是减吗？？？