为啥不查官方文档呢?

https://dev.mysql.com/doc/refman/8.4/en/problems-connecting.html

> After a fresh installation, if you try to log on to the server as root without using a password, you might get the following error message.(全新安装后，如果您尝试以不使用密码的方式登录服务器 root ，则可能会收到以下错误消息。)
```
$> mysql -u root
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)
```

> If you get the following error, it means that you are using an incorrect root password (如果出现以下错误，则表示您使用的 root 密码不正确)
```
$> mysqladmin -u root -pxxxx ver
Access denied for user 'root'@'localhost' (using password: YES)
```

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