MySql Timestamp默认值限制问题

今天在往mysql表中新增一列timestamp时，希望设置默认值为0，结果发现居然提示失败，记录一下

# 问题记录

测试的mysql版本为 5.7.24

创建要给测试的表用来说明

mysql> show create table demo\G
*************************** 1. row ***************************
       Table: demo
Create Table: CREATE TABLE `demo` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `age` int(10) NOT NULL DEFAULT '0',
  `name` varchar(30) NOT NULL DEFAULT '',
  PRIMARY KEY (`id`),
  KEY `UNI_AGE` (`age`),
  KEY `name` (`name`)
) ENGINE=InnoDB AUTO_INCREMENT=9 DEFAULT CHARSET=utf8mb4
1 row in set (0.00 sec)

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我们希望在这个表里面，新增一列, 默认值为0（即对应的日期为1970-01-01 00:00:00）

mysql> alter table demo add column test_time timestamp not null default '1970-01-01 00:00:00';
ERROR 1067 (42000): Invalid default value for 'test_time'

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直接提示默认值非法，why?

官方说明： https://dev.mysql.com/doc/refman/5.7/en/datetime.html (opens new window)

The TIMESTAMP data type is used for values that contain both date and time parts. TIMESTAMP has a range of '1970-01-01 00:00:01' UTC to '2038-01-19 03:14:07' UTC.

默认值有限制，要求必须是>=1970-01-01 00:00:01 且 <=2038-01-19 03:14:07

然后我们再测试一下

mysql> alter table demo add column test_time timestamp not null default '1970-01-01 00:00:01';
ERROR 1067 (42000): Invalid default value for 'test_time'

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依然是失败!!! why？

注意上面说的时间是utc日期，而我们大中华是utc8

所以我们需要把时间设置为8:00:01

mysql> alter table demo add column test_time timestamp not null default '1970-01-01 08:00:01';
Query OK, 0 rows affected (0.18 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> show create table demo\G
*************************** 1. row ***************************
       Table: demo
Create Table: CREATE TABLE `demo` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `age` int(10) NOT NULL DEFAULT '0',
  `name` varchar(30) NOT NULL DEFAULT '',
  `test_time` timestamp NOT NULL DEFAULT '1970-01-01 08:00:01',
  PRIMARY KEY (`id`),
  KEY `UNI_AGE` (`age`),
  KEY `name` (`name`)
) ENGINE=InnoDB AUTO_INCREMENT=9 DEFAULT CHARSET=utf8mb4
1 row in set (0.01 sec)