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怎么撤销mysql的操作 mysql撤销语句

mysql workbench怎么撤销动作

先FILE——Auto save,然后在FILE——restore就可以撤销的。

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怎么撤回MySQL“允许远程机器用root用户连接mysql数据库”的操作,回到默认值?

你应该是想禁止root的远程连接功能吧,如果是这样,可用采取如下办法:

1、修改root的远程权限

use mysql;

update user set host = "localhost" where user = "root" and host = "%";

flush privileges

2、修改mysql的连接端口,比如不要用默认的3306,改成其它不常用端口

MYSQL如何撤销check约束? 不要W3C里面的 ALTER TABLE Persons DROP CONSTRAINT chk_Person

对于非unique索引和外键可以可以设置禁用,其他的,暂时还没发现。

想要禁用非unique索引的话可以用:ALTER TABLE ... DISABLE KEYS,这个语句需要是MyISAM的表才行。

想要禁用外键的话可以用类似下面的语句:

mysql SET foreign_key_checks = 0;

mysql SOURCE dump_file_name;

mysql SET foreign_key_checks = 1;

详细的说明,可以参考mysql文档,这里贴两段摘自MySql 5.6版的英文说明,帮助理解。

If you use ALTER TABLE on a MyISAM table, all nonunique indexes are created in a separate batch (as for REPAIR TABLE). This should make ALTER TABLE much faster when you have many indexes.This feature can be activated explicitly for a MyISAM table. ALTER TABLE ... DISABLE KEYS tells MySQL to stop updating nonunique indexes. ALTER TABLE ... ENABLE KEYS then should be used to re-create missing indexes. MySQL does this with a special algorithm that is much faster than inserting keys one by one, so disabling keys before performing bulk insert operations should give a considerable speedup. Using ALTER TABLE ... DISABLE KEYS requires the INDEX privilege in addition to the privileges mentioned earlier.While the nonunique indexes are disabled, they are ignored for statements such as

SELECT and EXPLAIN that otherwise would use them.

To make it easier to reload dump files for tables that have foreign key relationships,

mysqldump automatically includes a statement in the dump output to set

foreign_key_checks to 0. This avoids problems with tables having to be reloaded in a particular order when the dump is reloaded. It is also possible to set this variable manually:mysql SET foreign_key_checks = 0;

mysql SOURCE dump_file_name;

mysql SET foreign_key_checks = 1;

This enables you to import the tables in any order if the dump file contains tables that are not correctly ordered for foreign keys. It also speeds up the import operation. Setting

foreign_key_checks to 0 can also be useful for ignoring foreign key constraints during LOAD DATA and ALTER TABLE operations. However, even ifforeign_key_checks = 0

, InnoDB does not permit the creation of a foreign key constraint where a column references a nonmatching column type. Also, if an InnoDB table has foreign key constraints,

ALTER TABLE cannot be used to change the table to use another storage engine. To alter the storage engine, drop any foreign key constraints first.

怎么撤回MySQL中“update user set host ='%' where user ='root'”的操作,恢复到默认值权限

一般MySQL中默认的host是localhost,可以以root用户登录MySQL,连接mysql数据库,运行命令:select user,host from user; 查看各用户的host

既然已经更新过了,可以再运行命令:update user set host ='localhost' where user ='root'; 修改会默认的host就行了,其中“%”表示允许所有机器能访问root用户。

使用mysql时候不小心多update了数据,想问一下如何才能够返回上一步?

1、首先:创建一个表格,插入数据。

2、查看一下表格插入的所有数据。

3、用update 的命令修改wulianwang2改为wulianwang3看图,这是根据id的位置进行查找的。

4、查看刚刚修改有没有成功,也是用到刚刚的查询语句。

5、其实就是增加了一些修改的条件,刚刚只是修改一个值,现在改为两个值也是可行的,两个值之间都好隔开,其他不变。

6、最后查看修改后的表,就完成了。


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