最重要的一步，先把所有的数据库备份下来

参考《## 使用mysqldump的--all-databases参数完整备份数据库时如何排除掉某些不需要备份的库？》

完整删除原来的mysql5.7

1. 打开控制台
2. 备份数据
3. 用这个命令查看mysql的进程: ps -ax | grep mysql
4. 停止&kill掉所有的mysql进程
5. 用brew删除mysql@5.7:

   brew remove mysql
   brew cleanup
   

6. 删除文件:

   sudo rm /usr/local/mysql
   sudo rm -rf /usr/local/var/mysql
   sudo rm -rf /usr/local/mysql*
   sudo rm ~/Library/LaunchAgents/homebrew.mxcl.mysql.plist
   sudo rm -rf /Library/StartupItems/MySQLCOM
   sudo rm -rf /Library/PreferencePanes/My*
   

7. 删除mysql的启动项:

   launchctl unload -w ~/Library/LaunchAgents/homebrew.mxcl.mysql.plist
   

8. 删除配置文件(如果没有就跳过):

   # Edit this file: /etc/hostconfig
   # Remove the line MYSQLCOM=-YES-
   

9. 删除原mysql的一些设置:

   rm -rf ~/Library/PreferencePanes/My*
   sudo rm -rf /Library/Receipts/mysql*
   sudo rm -rf /Library/Receipts/MySQL*
   sudo rm -rf /private/var/db/receipts/*mysql*
   

10. 重启电脑并确认已经成功清空原mysql
11. 用brew install mysql安装新版的mysql8
12. 安装完成后运行命令：mysql.server start启动mysql
13. 注意修改mysql的环境变量：export PATH="/usr/local/opt/mysql/bin$PATH"
14. 先修改root密码：mysqladmin -u root password 'yourpassword'
15. 安全设置mysql_secure_installation

安全设置示例：

Securing the MySQL server deployment**.**

Enter password **for** user root**:**

**VALIDATE** **PASSWORD** **COMPONENT** can be used to test passwords
and improve security**.** It checks the strength **of** password
and allows the users to **set** only those passwords which are
secure enough**.** Would you like to setup **VALIDATE** **PASSWORD** component**?**

Press y**|****Y** **for** Yes**,** any other key **for** **No****:** no
#这里我选了不安全密码强度验证插件

Using existing password **for** root**.**
Change the password **for** root **?** **(****(**Press y**|****Y** **for** Yes**,** any other key **for** No**)** **:** no
#这里我选了不修改root密码
 **...** skipping**.**

By **default****,** a MySQL installation has an anonymous user**,**
allowing anyone to log into MySQL without having to have
a user account created **for** them**.** This is intended only **for**
testing**,** and to make the installation go a bit smoother**.**
You should remove them before moving into a production
environment**.**

Remove anonymous users**?** **(**Press y**|****Y** **for** Yes**,** any other key **for** No**)** **:** y
Success**.**
#这里我选择了移除匿名用户


Normally**,** root should only be allowed to connect **from**
**'localhost'****.** This ensures that someone cannot guess at
the root password from the network**.**

Disallow root login remotely**?** **(**Press y**|****Y** **for** Yes**,** any other key **for** No**)** **:** y
Success**.**
#这里我选择了禁用root账号远程登录访问

By **default****,** MySQL comes **with** a database named **'test'** that
anyone can access**.** This is also intended only **for** testing**,**
and should be removed before moving into a production
environment**.**

Remove test database and access to it**?** **(**Press y**|****Y** **for** Yes**,** any other key **for** No**)** **:** no
 **...** skipping**.**
 #这里我选择了不移除测试数据库

Reloading the privilege tables will ensure that all changes
made so far will take effect immediately**.**

Reload privilege tables now**?** **(**Press y**|****Y** **for** Yes**,** any other key **for** No**)** **:** y
Success**.**
#这里我选择了重新加载权限表，因为我前面选择了禁用root账号远程登录访问

All done**!**

提示

brew安装后MYSQL的配置文件my.cnf位置为：/usr/local/etc/my.cnf没有可以自己创建
数据目录为：/usr/local/var/mysql

常用命令

启动：sudo mysql.server start 或者 brew services start mysql
关闭：sudo mysql.server stop 或者 brew services stop mysql
重启：sudo mysql.server restart 或者 brew services restart mysql
连接：mysql -u root -p
开机启动：brew services start mysql

注意：使用brew services可以把mysql注册为开机自动启动的系统服务在后台常驻运行，此方法适用于任何使用Homebrew安装的服务
使用mysql自带的mysql.server启动，但电脑重启后mysql服务不会自动启动

解决错误

用Navicat Premium尝试连接刚安装的MYSQL服务报如下错误：

Authentication plugin 'caching_sha2_password' cannot be loaded: dlopen(/usr/local/mysql/lib/plugin/caching_sha2_password.so, 2): image not found

先修改my.cnf：

在[mysqld]块增加下面两行代码：

[caching_sha2_password]

default_authentication_plugin= mysql_native_password

重启MYSQL服务： sudo mysql.server restart

然后进入mysql:

执行命令：FLUSH PRIVILEGES;