> All those bloomin' bindings for the same packages!  Everybody's got to 
> go around repeating themselves always!  What's it all for!

MySQL/Ruby[1] is a C extension for Ruby that compiles against the MySQL 
client library. This is the fastest approach, but requires compilation 
and access to libmysqlclient.so.

Ruby/MySQL[2] is a native Ruby solution with the same API as MySQL/Ruby 
(and also written by Tomita Masahiro). So this doesn't require any 
compilation or access to libmysqlclient.so.

DBI/DBD[3] sits on top of MySQL/Ruby and adds a bit of convenience and 
a uniform interface that'll let you switch from MySQL to any of the 
other databases supported by the package.

In my unscientific test, I've found MySQL/Ruby to be by far the 
fastest. Ruby/MySQL and DBI/DBD are about 50% slower. But that might 
not matter too much depending on your situation.

[1] http://www.tmtm.org/en/mysql/ruby/
[2] http://www.tmtm.org/en/ruby/mysql/
[3] http://ruby-dbi.sourceforge.net/
--
David Heinemeier Hansson,
http://www.basecamphq.com/   -- Web-based Project Management
http://www.loudthinking.com/ -- Broadcasting Brain