I really wanted to get MySQL logging all the queries rails was producing. After a good hour of messing around I have cracked it!
Mac OS X has a startup file which starts mysql on startup. This needs to be modified to turn on logging support.
This can be found in /Library/StartupItems/MySQLCOM. The file required editing is MySQLCOM. Open it up using your favorite text editor. The the StartService() method, and then after the start command add
To create the log file, use the following commands
sudo cd /var/log
sudo touch mysqld.log
sudo chown mysql mysqld.log
Once that has been done, restart the server
sudo /Library/StartupItems/MySQLCOM/./MySQLCOM restart
You can then tail the log file and see all the queries in real time
tail -f mysqld.log
Bobs your uncle! Done