mysql相关 timestamp遇到的小问题

DROP TABLE IF EXISTS `user_log`;

CREATE TABLE `user_log` (

  `id` int(11) NOT NULL AUTO_INCREMENT COMMENT '主键id',

  `o_id` char(24) NOT NULL COMMENT '订单id号',

  `uid` int(10) unsigned NOT NULL COMMENT '用户ID',

  `note` varchar(255) NOT NULL DEFAULT '' COMMENT '取消原因',

  `time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,

  PRIMARY KEY (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COMMENT='订单表';

 `time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,

注意这句话