If you want to create a Rails application with MySQL on Windows, you may face the following problems (which i had). I hope, this post helps you.

First when starting the application, i got the message “no libmysql.dll found”. This can be resolved by copying libmysql.dll from your MySQL installation to the ${rubyinstallation}/bin directory.

But then i got another problem: “Incorrect MySQL client library version! This gem was compiled for 6.0.0 but the client library is 5.5.27.” I installed all my gems with bundler, so i didn’t get a very important message from gem: <div class="well"> You’ve installed the binary version of mysql2.
It was built using MySQL Connector/C version 6.0.2.
It’s recommended to use the exact same version to avoid potential issues.

At the time of building this gem, the necessary DLL files where available
in the following download:

http://dev.mysql.com/get/Downloads/Connector-C/mysql-connector-c-noinstall-6.0.2-win32.zip/from/pick

And put lib\libmysql.dll file in your Ruby bin directory, for example C:\Ruby\bin </div>

The solution is here to download the zip and copy the libmysql.dll file from there. Then the access to MySQL from the Rails application should work.