How to start/stop/restart MySQL in Mac OS X? Very easy!
In OS X Yosemite / El Capitan (MySQL post 5.7) run in terminal:
sudo launchctl load -F /Library/LaunchDaemons/com.oracle.oss.mysql.mysqld.plist
Note: This is a persistent setting which means that MySQL will automatically start on the next OS X start.
sudo launchctl unload -F /Library/LaunchDaemons/com.oracle.oss.mysql.mysqld.plist
In OS X pre Yosemite (MySQL pre 5.7) run in terminal:
sudo /usr/local/mysql/support-files/mysql.server start
sudo /usr/local/mysql/support-files/mysql.server stop
sudo /usr/local/mysql/support-files/mysql.server restart
Quite easy :-)