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  • 关于MySQL数据类型timestamp的讨论

    在项目中用到了timestamp这个类型,该字段本意是用于存储改行记录的创建时间的,实际上这是一个很危险的设置;

    mysql官方文档上有这么一段话:

    The TIMESTAMP data type provides a type that you can use to automatically mark INSERT or UPDATE operations with the current date and time. If you have multiple TIMESTAMP columns in a table, only the first one is updated automatically. (From MySQL 4.1.2 on, you can specify which TIMESTAMP column updates;

    意思大概是timestamp类型会随着insert或update更新而自动更新;

    下面实际来测试一个案例:

    mysql> create table b(ID int ,Time timestamp);
    Query OK, 0 rows affected (0.01 sec)

    mysql> insert into b values(1,now());
    Query OK, 1 row affected (0.00 sec)

    mysql> insert into b values(2,now());
    Query OK, 1 row affected (0.01 sec)

    -------------------------------------------------

    mysql> select * from b;
    +------+---------------------+
    | ID   | Time                |
    +------+---------------------+
    |    1 | 2013-07-26 13:56:11 |
    |    2 | 2013-07-26 13:57:43 |
    +------+---------------------+

    ------------------------------------------------

    mysql> update b  set  id=3 where id=2;

    ------------------------------------------------

    mysql> select * from b;
    +------+---------------------+
    | ID   | Time                |
    +------+---------------------+
    |    1 | 2013-07-26 13:56:11 |
    |    3 | 2013-07-26 16:35:43 |
    +------+---------------------+

    可以看出timestamp自动更新了;更多timestamp的信息可以查看mysql官方文档http://dev.mysql.com/doc/refman/4.1/en/timestamp-pre-4-1.html

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  • 原文地址:https://www.cnblogs.com/simplelogic/p/3217419.html
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