如果你没有足够的特权，就会发生这种情况。

输入su，输入root密码后重试。

我找到的所有解决方案都比必要的要复杂得多，没有一个适合我。这是解决我问题的办法。不需要重新启动mysqld或使用特殊权限启动它。

sudo mysql

-- for MySQL
ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY 'root';

-- for MariaDB
ALTER USER 'root'@'localhost' IDENTIFIED VIA mysql_native_password USING PASSWORD('root');

通过一个查询，我们将auth_plugin更改为mysql_native_password，并将根密码设置为root(可以在查询中随意更改)。

现在您应该可以使用root登录了。更多信息可以在MySQL文档或MariaDB文档中找到。

(使用Ctrl + D或输入Exit退出MySQL控制台。)

我这样做是为了在OS x中MySQL的初始设置中设置我的根密码。

sudo sh -c 'echo /usr/local/mysql/bin > /etc/paths.d/mysql'

关闭终端并打开一个新终端。

在Linux中，可以使用以下方法设置根密码。

sudo /usr/local/mysql/support-files/mysql.server stop
sudo mysqld_safe --skip-grant-tables

(sudo mysqld_safe——skip-grant-tables:第一次对我不起作用。但在第二次尝试时，成功了。)

然后登录MySQL:

mysql -u root

FLUSH PRIVILEGES;

现在修改密码:

ALTER USER 'root'@'localhost' IDENTIFIED BY 'newpassword';

重新启动MySQL:

sudo /usr/local/mysql/support-files/mysql.server stop
sudo /usr/local/mysql/support-files/mysql.server start

在尝试了所有其他答案后，这是最后对我有用的:

sudo mysql -- It does not ask me for any password

-- Then in MariaDB/MySQL console:
update mysql.user set plugin = 'mysql_native_password' where User='root';
FLUSH PRIVILEGES;
exit;

我发现答案在博客文章解决:错误“访问拒绝用户' root ' @ ' localhost '”的MySQL - codementor。科技(媒介)。

之前的答案都没有帮助我解决这个问题，所以这里是我找到的解决方案。

相关部分:

In Ubuntu systems running MySQL 5.7 (and later versions), the root MySQL user is set to authenticate using the auth_socket plugin by default rather than with a password. This allows for some greater security and usability in many cases, but it can also complicate things when you need to allow an external program (e.g., phpMyAdmin) to access the user. In order to use a password to connect to MySQL as root, you will need to switch its authentication method from auth_socket to mysql_native_password. To do this, open up the MySQL prompt from your terminal: sudo mysql Next, check which authentication method each of your MySQL user accounts use with the following command: SELECT user,authentication_string,plugin,host FROM mysql.user; Output +------------------+-------------------------------------------+-----------------------+-----------+ | user | authentication_string | plugin | host | +------------------+-------------------------------------------+-----------------------+-----------+ | root | | auth_socket | localhost | | mysql.session | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE | mysql_native_password | localhost | | mysql.sys | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE | mysql_native_password | localhost | | debian-sys-maint | *CC744277A401A7D25BE1CA89AFF17BF607F876FF | mysql_native_password | localhost | +------------------+-------------------------------------------+-----------------------+-----------+ 4 rows in set (0.00 sec) In this example, you can see that the root user does in fact authenticate using the auth_socket plugin. To configure the root account to authenticate with a password, run the following ALTER USER command. Be sure to change password to a strong password of your choosing, and note that this command will change the root password you set in Step 2: ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY 'password'; Then, run FLUSH PRIVILEGES which tells the server to reload the grant tables and put your new changes into effect: FLUSH PRIVILEGES; Check the authentication methods employed by each of your users again to confirm that root no longer authenticates using the auth_socket plugin: SELECT user,authentication_string,plugin,host FROM mysql.user; Output +------------------+-------------------------------------------+-----------------------+-----------+ | user | authentication_string | plugin | host | +------------------+-------------------------------------------+-----------------------+-----------+ | root | *3636DACC8616D997782ADD0839F92C1571D6D78F | mysql_native_password | localhost | | mysql.session | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE | mysql_native_password | localhost | | mysql.sys | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE | mysql_native_password | localhost | | debian-sys-maint | *CC744277A401A7D25BE1CA89AFF17BF607F876FF | mysql_native_password | localhost | +------------------+-------------------------------------------+-----------------------+-----------+ 4 rows in set (0.00 sec) You can see in this example output that the root MySQL user now authenticates using a password. Once you confirm this on your own server, you can exit the MySQL shell: exit

在你的MySQL Workbench中，你可以到左边的侧边栏，在Management下选择“Users and Privileges”，在User Accounts下点击root，在右边的部分点击tab“Account Limits”增加最大查询，更新等，然后点击tab“Administrative Roles”，勾选复选框赋予该帐户访问权限。