Oh what trouble Rails 2.2 and MySQL (on Mac OS X) can be. Rails, as of version >= 2.2, no longer comes bundled with the MySQL adapter. This means you'll need to install it yourself, but it appears that the gem for installing it is also broken.
This will fail
gem install mysql
What you need to do is tell the gem which MySQL to use. I installed MySQL with mac ports, http://macports.org , so I need to specify this when I run the installation command.
gem install mysql -- --with-mysql-config=/opt/local/lib/mysql5/bin/mysql_configCheck out an earlier post explaining how to install MySQL with mac ports http://seanbehan.com/programming/installing-sphinx-search-engine-on-mac-os-x-or-ld-library-not-found-for-lmysqlclient/
You're not out of the woods yet. Rails needs to know the location of the socket it uses to connect to the MySQL server. I created a symbolic link to the location Rails normally looks for this socket. You could specify the location of the socket in the config/database.yml file, however, then you'll need to do this with each of your applications.
ln -s /private/tmp/mysql.sock /opt/local/var/run/mysql5/mysqld.sock
If there is an easier way to get MySQL back for Rails on Mac OS X please let me know. I'd love a quick fix to this problem.