无法将tinyint和varchar字段更新为默认值null和空字符串

CREATE TABLE `tablename` (
  `id` bigint(15) NOT NULL AUTO_INCREMENT,
  `uuid` varchar(400) NOT NULL,
  `pre_notif_action` varchar(30) DEFAULT '',
  `pre_notif_interval` tinyint(1) DEFAULT NULL,
PRIMARY KEY (`id`),
UNIQUE KEY `uuid_UNIQUE` (`uuid`),

  ) ENGINE=InnoDB DEFAULT CHARSET=latin1

对于现有记录,分别在pre\u notif\u action和pre\u notif\u interval字段中使用值“predeactivate”和45-

mysql> select pre_notif_action, pre_notif_interval 
       from tablename 
       where uuid="1887826113857166800";

结果-

+------------------+--------------------+
| pre_notif_action | pre_notif_interval |
+------------------+--------------------+
| predeactivate    |                 45 |
+------------------+--------------------+

当我尝试编辑时,得到的是非零影响行-

 update prepaid_account 
 set pre_notif_action="" 
     and pre_notif_interval=NULL 
 where  uuid="1887826113857166800";

Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0

但是,当我选择-

mysql> select pre_notif_action, pre_notif_interval 
       from prepaid_account 
       where uuid="1887826113857166800";

+------------------+--------------------+
| pre_notif_action | pre_notif_interval |
+------------------+--------------------+
| 0                |                 45 |
+------------------+--------------------+