An error occurred while installing mysql2 (0.3.11)

@Ricardo Masao Shigeoka for the mac ,try first

brew install mysql, then

Put in your Gemfile gem 'mysql2', '0.3.18'

run bundle command in terminal.

This setup worked for me, I have El Captain OS, rails 4.2.6, hope this helps

try it

sudo apt-get install mysql-client libmysqlclient-dev