Remove Existing MySQL Installations (See related posts)

If you already have MySQL installed and used the package installer from MySQL to install it, you need to remove a single file (actually a symlink) to disable it:

sudo rm /usr/local/mysql

If you also installed the StartupItem package, you’ll want to remove it as well. Keep in mind that if you ever want to auto-start the old version of MySQL later on, you’ll need to re-download the package installer and reinstall the StartupItem.

sudo rm -rf /Library/StartupItems/MySQLCOM/