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DateTime A date and time combination. The supported range is '1000-01-01 0' to '9999-12-31 23:59:59'. MySQL displays DATETIME values in 'YYYY-MM-DD HH:MM:SS' format, but allows you to assign values to DATETIME columns using either strings or numbers. TimeStamp A timestamp. The range is '1970-01-01 0' to partway through the year 2037. A TIMESTAMP column is useful for recording the date and time of an INSERT or UPDATE operation. The first TIMESTAMP column in a table is automatically set to the date and time of the most recent operation if you don't assign it a value yourself. You can also set any TIMESTAMP column to the current date and time by assigning it a NULL value.
现在开始具体比较：DATETIME，字节数为8，取值范围为[1000-01-01 0——9999-12-31 23:59:59]
对应 Java 类型为java.sql.Timestamp
INSERT或UPDATE操作时 系统 不会自动修改其值，不可以设定默认值，为必须字段时必须手动插入，建议使用：new()
MySql按照YYYY-MM-DD HH:MM:SS对数据进行格式化，允许以字符串和数字的方式提交
eg：insert into time_table(CreateDate) values(‘2014-06-09 15:01:01’)
或insert into time_table(CreateDate) values(‘20140609150101’)
TIMESTAMP，字节数为4，取值范围为[19700101080001——20380119111407]
对应Java类型为java.sql.Timestamp
INSERT或UPDATE操作时（且未手动赋值）系统会自动更新、插入当前系统时间，默认值为CURRENT_TIMESTAMP()
使用TIMESTAMP一定要注意他的时间范围（见上）。
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