mysql user表没有了的解决办法：1、在“[mysqld]”中添加“skip-grant-tables”；2、编辑my.cnf配置文件，添加“sql_mode=NO_ENGINE_SUBSTITUTION”；3、重启mysql服务。

本文操作环境：Windows7系统，mysql5.5版，Dell G3电脑。

mysql user表没有了怎么办？

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 123456
mysql> 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> quit
Bye

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> exit
Bye

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_SUBSTITUTION
skip-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> exit
Bye

• 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！