It was difficult for me with this ... I tried all the answers above, so I can not determine exactly which combination led to the correction. I already installed mysql and reinstalled it from the mysql site. Finally he started working after I followed him.
This is on Mavericks using rails 4 and brew installed
brew install mysql
I do not recommend this process. Just noting that it worked for me after hours of disappointment.
ln -sfv /usr/local/opt/mysql/*.plist ~/Library/LaunchAgents launchctl load ~/Library/LaunchAgents/homebrew.mxcl.mysql.plist sudo gem uninstall mysql gem uninstall mysql2 gem install mysql gem install mysql2
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