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mysql 更新完密码，总是拒绝连接、登录失败?MySQL8.0 不能通过直接修改 mysql.user 表来更改密码。正确更改密码的方式备注: 清空root密码
MySQL8.0 不能通过直接修改 mysql.user 表来更改密码。

因为authentication_string字段下只能是MySQL加密后的43位字符串密码，其他的导致错误。错误不报出，但是无法再登录mysql，总是会提示 无法认证。
参考：MySQL8.0

mysql> USE mysql;
Database changed
mysql> UPDATE user SET authentication_string="123456" WHERE user="root";
Query OK, 1 row affected (0.39 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> FLUSH privileges;  # 刷新保存
Query OK, 0 rows affected (0.13 sec)

mysql 5.7.9 之后取消了password 函数，authentication_string=password("123456") 会报错

C:\WINDOWS\system32>mysql -u root -p
Enter password: ******
ERROR 1045 (28000): Access denied for user ‘root’@‘localhost’ (using password: YES)
1234567891011121314
如果 你已经这样更改密码，并且导致了无法进入mysql。本人表示同情之时，还为了你提供了详细的解决方案。请查看本文备注：清空root 密码
正确更改密码的方式

ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY "your_password";
mysql> USE mysql;
Database changed
mysql> ALTER USER 'root'@'localhost' IDENTIFIEED WITH mysql_native_password BY "markjun";
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'IDENTIFIEED WITH mysql_native_password BY "markjun"' at line 1
mysql> ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY "markjun";
Query OK, 0 rows affected (0.18 sec)

mysql> ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY "123456";
Query OK, 0 rows affected (0.08 sec)

mysql> SELECT user, authentication_string FROM user;
+------------------+------------------------------------------------------------------------+
| user             | authentication_string                                                  |
+------------------+------------------------------------------------------------------------+
| mysql.infoschema | $A$005$THISISACOMBINATIONOFINVALIDSALTANDPASSWORDTHATMUSTNEVERBRBEUSED |
| mysql.session    | $A$005$THISISACOMBINATIONOFINVALIDSALTANDPASSWORDTHATMUSTNEVERBRBEUSED |
| mysql.sys        | $A$005$THISISACOMBINATIONOFINVALIDSALTANDPASSWORDTHATMUSTNEVERBRBEUSED |
| root             | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9                              |
+------------------+------------------------------------------------------------------------+
4 rows in set (0.00 sec)

mysql> FLUSH privileges;
Query OK, 0 rows affected (0.38 sec)

mysql> quit;
Bye

F:\MySQL\mysql-8.0.13-winx64\bin>mysql -u root -p
Enter password: *******
...

mysql>

• 备注: 清空root密码

  停止 MySQL 任务 net stop MySQL

  mysqld 命令 mysqld –console –skip-grant-tables –shared-memory

  无密码进入mysql mysql -u root

  清空root 密码 UPDATE user SET authentication_string=”” WHERE user=“root”;

另一个终端无密码进入

F:\MySQL\mysql-8.0.13-winx64\bin>mysql -u root -p
Enter password: *******
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES)

F:\MySQL\mysql-8.0.13-winx64\bin>mysql -u root
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 7
...
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> USE mysql;
Database changed

mysql> SELECT user, authentication_string FROM user;
+------------------+------------------------------------------------------------------------+
| user             | authentication_string                                                  |
+------------------+------------------------------------------------------------------------+
| mysql.infoschema | $A$005$THISISACOMBINATIONOFINVALIDSALTANDPASSWORDTHATMUSTNEVERBRBEUSED |
| mysql.session    | $A$005$THISISACOMBINATIONOFINVALIDSALTANDPASSWORDTHATMUSTNEVERBRBEUSED |
| mysql.sys        | $A$005$THISISACOMBINATIONOFINVALIDSALTANDPASSWORDTHATMUSTNEVERBRBEUSED |
| root             | 123456                                                                |
+------------------+------------------------------------------------------------------------+
4 rows in set (0.34 sec)

mysql> UPDATE user SET authentication_string="" WHERE user="root";
Query OK, 1 row affected (0.20 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> SELECT user, authentication_string FROM user;
+------------------+------------------------------------------------------------------------+
| user             | authentication_string                                                  |
+------------------+------------------------------------------------------------------------+
| mysql.infoschema | $A$005$THISISACOMBINATIONOFINVALIDSALTANDPASSWORDTHATMUSTNEVERBRBEUSED |
| mysql.session    | $A$005$THISISACOMBINATIONOFINVALIDSALTANDPASSWORDTHATMUSTNEVERBRBEUSED |
| mysql.sys        | $A$005$THISISACOMBINATIONOFINVALIDSALTANDPASSWORDTHATMUSTNEVERBRBEUSED |
| root             |                                                                        |
+------------------+------------------------------------------------------------------------+
4 rows in set (0.00 sec)

mysql> FLUSH privileges;
Query OK, 0 rows affected (0.10 sec)

mysql> quit;
Bye

停止 mysqld 任务，Ctrl+C 结束任务，或者直接关闭 运行 mysqld 的 cmd 终端。

需要先停止运行上述 mysqld 任务,否则报错

F:\MySQL\mysql-8.0.13-winx64\bin>net start mysql
MySQL 服务正在启动 .
MySQL 服务无法启动。

服务没有报告任何错误。

请键入 NET HELPMSG 3534 以获得更多的帮助。

先停止上述 mysqld 任务

F:\MySQL\mysql-8.0.13-winx64\bin>net start mysql
MySQL 服务正在启动 ...
MySQL 服务已经启动成功。

现在 mysql root 已经没有了密码

F:\MySQL\mysql-8.0.13-winx64\bin>mysql -u root -p
Enter password:
Welcome to the MySQL monitor.  Commands end with ; or \g.

...
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql>