1.错误代码1251：mysql8 之前的版本中加密规则是mysql_native_password,而在mysql8之后,加密规则是caching_sha2_password, 所以需要把mysql用户登录密码加密规则还原成mysql_native_password

ALTER USER 'root'@'%' IDENTIFIED WITH mysql_native_password BY '123456';
flush privileges;