最近朋友问我一些MySQL用户的问题，就做了一些测试，记录如下：
一：用户的创建（两种方法）：
方法一：CREATE USER 'username'@'%' IDENTIFIED BY 'password';
方法二：GRANT select ON databasename.tablename TO 'username'@'%' ;
二：mysql root用户密码设置以及修改。
方法1： 用SET PASSWORD命令
mysql -u root
mysql> SET PASSWORD FOR 'root'@'localhost' = PASSWORD('newpass');
方法2：用mysqladmin
mysqladmin -u root password "newpass"
如果root已经设置过密码，采用如下方法
mysqladmin -u root password oldpass "newpass"
方法3： 用UPDATE直接编辑user表
mysql -u root
mysql> use mysql;
mysql> UPDATE user SET Password = PASSWORD('newpass') WHERE user = 'root';
mysql> FLUSH PRIVILEGES;
在丢失root密码的时候，可以这样
mysqld_safe --skip-grant-tables&
mysql -u root mysql
mysql> UPDATE user SET password=PASSWORD("new password") WHERE user='root';
mysql> FLUSH PRIVILEGES;
三：重点讲解创建mysql用户时，@后面的ip的意义：就是为了限制登陆mysql的ip，具体有如下：
1)只允许在本地登录；
mysql> CREATE USER 'liuwenhe'@'localhost' IDENTIFIED BY 'liuwenhelocal';
Query OK, 0 rows affected (0.00 sec)
2）允许在192.168.0网段登陆mysql；
mysql> CREATE USER 'liuwenhe'@'192.168.0.%' IDENTIFIED BY 'liuwenhe0';
Query OK, 0 rows affected (0.00 sec)
3）允许在192.168.8网段登陆mysql；
mysql> CREATE USER 'liuwenhe'@'192.168.8.%' IDENTIFIED BY 'liuwenhe8';
Query OK, 0 rows affected (0.00 sec)
4）没有限制，也就是可以在任何网络段登陆（前提是网络得通）；
mysql> CREATE USER 'liuwenhe'@'%' IDENTIFIED BY 'liuwenheall';
Query OK, 0 rows affected (0.00 sec)
针对上面这几个liuwenhe用户做了一些测试，结果如下：
1） 'liuwenhe'@'192.168.0.%'这类的用户是不能在本地登录的，要想在本地登录，需要有localhost或者127.0.0.1的登陆权限；
需要注意的是，如果你只创建了用户 'liuwenhe'@'localhost' ，
1.mysql> CREATE USER 'liuwenhe'@'localhost' IDENTIFIED BY 'liuwenhelocal';
Query OK, 0 rows affected (0.00 sec)
mysql> select host,user from mysql.user;
+--------------+----------+
| host | user |
+--------------+----------+
| % | ogg |
| % | root |
| 127.0.0.1 | root |
| 192.168.0.% | ncms |
| 192.168.0.13 | rep |
| localhost | liuwenhe |
| localhost | ncms |
| localhost | ogg |
| localhost | root |
| server01 | root |
+--------------+----------+
10 rows in set (0.00 sec)
如下两种登陆方式都能成功：
[root@server02 ~]# mysql -uliuwenhe -pliuwenhelocal -hlocalhost
[root@server02 ~]# mysql -uliuwenhe -pliuwenhelocal -h127.0.0.1
2.如果你只创建了liuwenhe'@'l127.0.0.1'，
mysql> select host,user from mysql.user;
+--------------+----------+
| host | user |
+--------------+----------+
| % | ogg |
| % | root |
| 127.0.0.1 | liuwenhe |
| 127.0.0.1 | root |
| 192.168.0.% | ncms |
| 192.168.0.13 | rep |
| localhost | ncms |
| localhost | ogg |
| localhost | root |
| server01 | root |
+--------------+----------+
10 rows in set (0.00 sec)
只能通过mysql -uliuwenhe -pliuwenhelocal -h127.0.0.1登陆，不能通过 mysql -uliuwenhe -pliuwenhelocal -hlocalhost登陆；
[root@server02 ~]# mysql -uliuwenhe -pliuwenhelocal -h127.0.0.1
Warning: Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 3628
Server version: 5.6.26-enterprise-commercial-advanced-log MySQL Enterprise Server - Advanced Edition (Commercial)
Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql>
不能通过localhost登陆，如下报错：
[root@server02 ~]# mysql -uliuwenhe -pliuwenhelocal -hlocalhost
Warning: Using a password on the command line interface can be insecure.
ERROR 1045 (28000): Access denied for user 'liuwenhe'@'localhost' (using password: YES)