我用以下方法解决了这个问题:

关闭MySQL服务器:MySQL。服务器停止 以安全模式运行MySQL: mysqld_safe——skip-grant-tables 在另一个终端，使用mysql -u root登录 在同一终端上运行UPDATE mysql。SET authentication_string=null WHERE user ='root';然后用exit退出; 使用mysql停止安全模式服务器。服务器停止后再正常启动;mysql。服务器启动

现在您可以使用

ALTER USER 'root'@'localhost' IDENTIFIED WITH caching_sha2_password BY 'yourpasswd';

$ export PATH=$PATH:/usr/local/mysql/bin

now,to make this permanent:
$ echo 'export PATH=$PATH:/usr/local/mysql/bin' >> ~/.bash_profile

next, start mysql in safe mode:
$ sudo mysqld_safe --skip-grant-tables;

If this does not work, go to System Preferences and stop MySQL server.
next, On the **other** terminal, you may use the below:

$ mysql -u root

mysql> USE mysql;

mysql> UPDATE mysql.user SET authentication_string=null WHERE 
User='root';

mysql> FLUSH PRIVILEGES;

mysql> exit;

$ mysql -u root
mysql> ALTER USER 'root'@'localhost' IDENTIFIED WITH 
caching_sha2_password BY 'yourpassword';

$ mysql -u root -p
Enter password: 
mysql> SELECT user();

next, start the mysql server in normal mode. and you're done with resetting your root password. this worked for mysql 8.0.17 ver. for me.
thanks to everyone on top, https://stackoverflow.com/questions/36099028/error-1064-42000-you-have-an-error-in-your-sql-syntax-want-to-configure-a-pa,

https://www.houseninetytwo.com/how-to-use-mysql-in-terminal-on-mac-os-high-sierra/: ~:文本=你% 5月20日% 20 % 20了% 20,% 2 fmysql % 2 fbin % 2 fmysql。= % 20应该% 20执行% 20 % 20对,返回% 20 % 20版本% % 20 mysql中的20个。

mysql网站上提供的说明非常清楚，比上面提到的还要清楚

$ sudo /usr/local/mysql/support-files/mysql服务器停止 $ sudo /usr/local/mysql/support-files/mysql服务器启动——skip-grant-tables /usr/local/mysql/bin/mysql mysql> FLUSH PRIVILEGES; mysql> ALTER USER 'root'@'localhost' IDENTIFIED BY 'MyNewPass'; mysql>退出或按Ctrl + z $ sudo /usr/local/mysql/support-files/mysql服务器停止 $ sudo /usr/local/mysql/support-files/mysql服务器启动 /usr/local/mysql/support-files/mysql -u root -p 输入新密码，即MyNewPass

参考:http://dev.mysql.com/doc/refman/5.7/en/resetting-permissions.html

点击这里阅读更多。

截至2022年12月，以下适用于macOS Big Sur 11.2.3上的MySQL 8.0.26:

去系统首选> mysql >停止服务器 打开终端并运行:mysqld_safe——skip-grant-tables 打开一个新终端，运行:mysql -u root 运行:ALTER USER 'root'@'localhost' IDENTIFIED BY 'root'; ROOT将是您的新密码。 运行:FLUSH特权; 运行:退出 进入系统首选项> mysql >启动服务器

macOS v10.14 (Mojave)及更高版本，从Mac OS X DMG安装程序安装5.7.26。

当尝试使用其他用户发布的UPDATE命令时，会导致以下错误:

错误1820 (HY000):在执行此语句之前，您必须使用ALTER USER语句重置密码。

复制安装程序提供给您的密码，打开终端，然后执行以下操作:

mysql -uroot -p
ALTER USER 'root'@'localhost' IDENTIFIED BY 'YOURPASSWORDHERE';

停止mysqld服务器。

Mac OS X:系统首选项→MySQL→停止MySQL服务器 Linux(从终端):sudo systemctl停止mysqld.service

Start the server in safe mode with privilege bypass From Terminal: sudo /usr/local/mysql/bin/mysqld_safe --skip-grant-tables In a new terminal window: sudo /usr/local/mysql/bin/mysql -u root This will open the MySQL command-line client. From here enter: UPDATE mysql.user SET authentication_string=PASSWORD('NewPassword') WHERE User='root'; FLUSH PRIVILEGES; quit Stop the mysqld server again and restart it in normal mode. Mac OS X (From Terminal): sudo /usr/local/mysql/support-files/mysql.server restart Linux Terminal: sudo systemctl restart mysqld