错误如图所示:

错误详情信息:

1251 client does not support authentication protocol requested by server;consider upgrading Mysql client

ERROR 1396 (HY000): Operation ALTER USER failed for 'root'@'localhost'

问题原因:
主要是由于mysql8以前的加密规则与mysql8以后的存在差异。

解决办法:

ALTER USER 'root'@'localhost' IDENTIFIED BY 'password' PASSWORD EXPIRE NEVER;  ##修改加密规则

ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY 'password'; ##更新一下用户的密码 password 为自己想要重新设置的密码

FLUSH PRIVILEGES; ##刷新权限

本文参考资料如下:
Navicat 连接 Mysql 出现1251错误