1： 使用set password语句修改

mysql> select user();
+----------------+
| user() |
+----------------+
| root@localhost |
+----------------+
1 row in set (0.08 sec)
 
mysql> set password=password('123456');
Query OK, 0 rows affected (0.00 sec)
 
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)
 
mysql> exit

2: 更新mysql数据库的user表

mysql> use mysql;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
 
Database changed
mysql> update user set password=PASSWORD('QwE123') where user='root';
Query OK, 4 rows affected (0.03 sec)
Rows matched: 4 Changed: 4 Warnings: 0
 
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)
 
mysql> quit

3：使用mysqladmin命令修改

命令一般为 mysqladmin -u root -p'oldpassword' password newpass 如下所示：

[root@DB-Server ~]# mysqladmin -u root -p'123456' password 'Qwe123'
Warning: Using a password on the command line interface can be insecure.

验证root密码修改是否成功

[root@DB-Server ~]# mysqladmin -u root -p'123456' password 'Qwe123'
Warning: Using a password on the command line interface can be insecure.

上面都是在知道root密码的情况下修改root密码，如果忘记了root密码，如何修改root的密码呢？

1：首先停掉MySQL服务

[root@DB-Server ~]# service mysql stop
Shutting down MySQL..[ OK ]
[root@DB-Server ~]# 

或

[root@DB-Server ~]# /etc/rc.d/init.d/mysql stop
Shutting down MySQL..[ OK ]

2：然后使用mysqld_safe命令启动mysql，更新root账号的密码

--skip-grant-tables：不启动grant-tables(授权表),跳过权限控制。

--skip-networking ：跳过TCP/IP协议，只在本机访问(这个选项不是必须的。可以不用)是可以不用

[root@DB-Server ~]# mysqld_safe --user=mysql --skip-grant-tables --skip-networking &
[1] 5145
You have new mail in /var/spool/mail/root
[root@DB-Server ~]# 150709 14:10:53 mysqld_safe Logging to '/var/lib/mysql/DB-Server.localdomain.err'.
150709 14:10:53 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql
 
[root@DB-Server ~]# mysql -u root mysql
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
 
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.6.20-enterprise-commercial-advanced MySQL Enterprise Server - Advanced Edition (Commercial)
 
Copyright (c) 2000, 2014, 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> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| test |
+--------------------+
4 rows in set (0.00 sec)
 
mysql> use mysql
Database changed
mysql> UPDATE user SET password=PASSWORD("Qwe123") WHERE user='root'; 
Query OK, 4 rows affected (0.01 sec)
Rows matched: 4 Changed: 4 Warnings: 0
 
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)
 
mysql> exit
Bye

3：重新启动MySQL服务。

以上所述就是本文的全部内容了，希望大家能够喜欢