I have the Ruby version ruby 1.9.2p0 (2010-08-18) [i386-mingw32] installed in Windows7. and the gem vesion 1.3.7
When i tried to install mysql gem, it is showing
If you are having this same problem in Linux, basically you just need to install a few libraries first. This worked for me.
> sudo apt-get install libmysql-ruby libmysqlclient-dev > gem install mysql
source: http://heatware.net/ruby-rails/solved-installing-mysql-gem-extconf-rb-failed-error/