本文操作环境：Windows7系统，mysql5.5版，Dell G3电脑。
mysql 忘记密码，重置密码，mysql.user表为空的解决办法：
一、用户表有用户，直接修改密码ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES)
修改mysql配置文件my.cnf：
vim /etc/my.cnf
在[mysqld]中添加
skip-grant-tables
重启mysql服务，用空密码直接登录，查询用户表，有结果则按如下步骤修改，结果为空直接最后的解决办法
mysql> select Host,User,authentication_string from mysql.user;+-----------+---------------+-------------------------------------------+| Host | User | authentication_string |+-----------+---------------+-------------------------------------------+| localhost | root | *6A7A490FB9DC8C33C2B025A91737077A7E9CC5E5 || localhost | mysql.session | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE || localhost | mysql.sys | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE || % | root | *6A7A490FB9DC8C33C2B025A91737077A7E9CC5E5 |+-----------+---------------+-------------------------------------------+4 rows in set (0.00 sec)
修改对应用户的密码
# 重置密码为 123456mysql> update mysql.user set authentication_string=password('123456') where user='root' Query OK, 2 rows affected, 1 warning (0.00 sec)Rows matched: 2 Changed: 2 Warnings: 1# 刷新权限，使配置生效mysql> FLUSH PRIVILEGES;Query OK, 0 rows affected (0.00 sec)# 退出mysql> quitBye取消或注释掉my.cnf配置文件添加的选项 skip-grant-tables ，重启mysql服务，搞定收工。
二、用户表没有数据，则需要插入用户数据mysql> select Host,User,authentication_string from mysql.user;Empty set (0.00 sec)# 退出登陆mysql> exitBye
编辑my.cnf配置文件，添加或修改下面两项（我这没有sql_mode项）：
sql_mode=NO_ENGINE_SUBSTITUTIONskip-grant-tables
停止mysql服务，启动数据库的安全模式：mysqld_safe &
使用root 空密码连接数据库： mysql -uroot -p
插入root用户数据
mysql> insert into mysql.user(Host,User,authentication_string) values("%","root",password("123456")); Query OK, 1 row affected, 4 warnings (0.00 sec)再次查询mysql.user表，会报错
mysql> select Host,User,authentication_string from mysql.user;ERROR 1194 (HY000): Table 'user' is marked as crashed and should be repaired
需要修复mysql.user表
mysql> REPAIR TABLE mysql.user;+------------+--------+----------+-------------------------------------------------+| Table | Op | Msg_type | Msg_text |+------------+--------+----------+-------------------------------------------------+| mysql.user | repair | info | Wrong bytesec: 113-108- 95 at 396; Skipped || mysql.user | repair | info | Found block that points outside data file at 32 || mysql.user | repair | info | Found block that points outside data file at 36 || mysql.user | repair | info | Found block that points outside data file at 40 || mysql.user | repair | info | Found block that points outside data file at 44 || mysql.user | repair | info | Found block that points outside data file at 48 || mysql.user | repair | info | Found block that points outside data file at 52 || mysql.user | repair | info | Found block that points outside data file at 56 || mysql.user | repair | info | Found block that points outside data file at 60 || mysql.user | repair | warning | Number of rows changed from 4 to 3 || mysql.user | repair | status | OK |+------------+--------+----------+-------------------------------------------------+11 rows in set (0.64 sec)# 再次查询user表mysql> select Host,User,authentication_string from mysql.user;+-----------+---------------+-------------------------------------------+| Host | User | authentication_string |+-----------+---------------+-------------------------------------------+| localhost | mysql.session | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE || localhost | mysql.sys | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE || % | root | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |+-----------+---------------+-------------------------------------------+3 rows in set (0.00 sec)
修改root用户的权限：
update mysql.user set `Select_priv` = 'Y', `Insert_priv` = 'Y', `Update_priv` = 'Y', `Delete_priv` = 'Y', `Create_priv` = 'Y', `Drop_priv` = 'Y', `Reload_priv` = 'Y', `Shutdown_priv` = 'Y', `Process_priv` = 'Y', `File_priv` = 'Y', `Grant_priv` = 'Y', `References_priv` = 'Y', `Index_priv` = 'Y', `Alter_priv` = 'Y', `Show_db_priv` = 'Y', `Super_priv` = 'Y', `Create_tmp_table_priv` = 'Y', `Lock_tables_priv` = 'Y', `Execute_priv` = 'Y', `Repl_slave_priv` = 'Y', `Repl_client_priv` = 'Y', `Create_view_priv` = 'Y', `Show_view_priv` = 'Y', `Create_routine_priv` = 'Y', `Alter_routine_priv` = 'Y', `Create_user_priv` = 'Y', `Event_priv` = 'Y', `Trigger_priv` = 'Y', `Create_tablespace_priv` = 'Y' where user='root';# 更新权限mysql> flush privileges;Query OK, 0 rows affected (0.00 sec)# 退出登陆mysql> exitBye
退出mysql，将my.cnf配置文件的修改恢复
结束mysqld_safe 进程：pkill mysql
启动mysql服务: systemctl start mysql
问题解决！
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