安装
brew install mysql
安装完其实会有一堆提示，按照提示操作即可。
这里记录一下，如果已经安装，但是mysql服务挂了，那么按照这个重新启动。
==> mysql
We've installed your MySQL database without a root password. To secure it run:
mysql_secure_installation
MySQL is configured to only allow connections from localhost by default
To connect run:
mysql -uroot
To have launchd start mysql now and restart at login:
brew services start mysql
Or, if you don't want/need a background service you can just run:
mysql.server start
