mysql timestamp 默認值當前時間

插入和更新時默認值爲當前時間，字段不能用Datetime類型，需要用timestamp類型，

建表時的寫法爲

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

DROP TABLE IF EXISTS `obj_Test`;
CREATE TABLE `obj_Test` (
  `ID` bigint(20) unsigned NOT NULL AUTO_INCREMENT,  ,
  `InsertTime` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  `ReasonCode` smallint(2) DEFAULT NULL,
 PRIMARY KEY (`ID`) 
) ENGINE=InnoDB AUTO_INCREMENT=96 DEFAULT CHARSET=utf8;