After a few tries in removing mysql 6.0 alpha (!) I found two useful sites with great answers.
Here they are:
Here are the extracts from these sites:
First step: host config
1.1. Open Terminal
1.2. sudo nano /etc/hostconfig
1.3. Enter your password if you’re not authed yet.
1.4. Delete the following line: “MYSQLCOM=-YES-”
1.5. CTRL+X (This is the command for closing NANO, Enter the “Y” key to save the file and exit nano).
Second step: removing folders
Make sure MySQL is not running.
sudo rm /usr/local/mysql
sudo rm -rf /usr/local/mysql*
sudo rm -rf /Library/StartupItems/MySQLCOM
sudo rm -rf /Library/PreferencePanes/My*
sudo rm -rf /Library/Receipts/mysql*
sudo rm -rf /Library/Receipts/MySQL*
sudo rm /etc/my.cnf
This first part didn’t work for me… so I found the next thing:
sudo rm -rf /var/db/receipts/com.mysql.*