转载自 https://www.cnblogs.com/shiysin/p/shiysin.html
Navicat连接不上，总是报错1251；
原因是MySQL8.0版本的加密方式和MySQL5.0的不一样，连接会报错。
更改加密方式
1.先通过命令行进入mysql的root账户：
PS C:\Windows\system32> mysql -uroot -p
再输入root的密码：
Enter password: ******
Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 18 Server version: 8.0.11 MySQL Community Server - GPL Copyright (c) 2000, 2018, 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>
2.更改加密方式：
mysql> ALTER USER ‘root‘@‘localhost‘ IDENTIFIED BY ‘password‘ PASSWORD EXPIRE NEVER; Query OK, 0 rows affected (0.10 sec)
3.更改密码：
mysql> ALTER USER ‘root‘@‘localhost‘ IDENTIFIED WITH mysql_native_password BY ‘password‘; Query OK, 0 rows affected (0.35 sec)
4.刷新：
mysql> FLUSH PRIVILEGES; Query OK, 0 rows affected (0.28 sec)
原文：https://www.cnblogs.com/dmfcjd/p/9019858.html