Mac OS X(10.9.3)にhomebrewでmysql5.5をインストール

$  brew install mysql

をするとmysql5.6が入るので(20140711現在)

$  brew tap homebrew/versions
$  brew install mysql55
==> Downloading http://downloads.mysql.com/archives/mysql-5.5/mysql-5.5.30.tar.gz
Already downloaded: /Library/Caches/Homebrew/mysql55-5.5.30.tar.gz
==> cmake . -DCMAKE_INSTALL_PREFIX=/usr/local/Cellar/mysql55/5.5.30 -DMYSQL_DATADIR=/usr/
==> make
==> make install
==> Caveats
A "/etc/my.cnf" from another install may interfere with a Homebrew-built
server starting up correctly.

To connect:
    mysql -uroot

This formula is keg-only, so it was not symlinked into /usr/local.

Conflicts with mysql, mariadb, percona-server, mysql-cluster, etc.

Generally there are no consequences of this for you. If you build your
own software and it requires this formula, you'll need to add to your
build variables:

    LDFLAGS:  -L/usr/local/opt/mysql55/lib
    CPPFLAGS: -I/usr/local/opt/mysql55/include


To reload mysql55 after an upgrade:
    launchctl unload ~/Library/LaunchAgents/homebrew.mxcl.mysql55.plist
    launchctl load ~/Library/LaunchAgents/homebrew.mxcl.mysql55.plist
==> Summary
  /usr/local/Cellar/mysql55/5.5.30: 6406 files, 220M, built in 4.4 minutes

$  brew link mysql55 --force                                                  
Linking /usr/local/Cellar/mysql55/5.5.30... 134 symlinks created

$ sudo mysql_install_db --verbose --user=`whoami` --basedir=/usr/local/Cellar/mysql55/5.5.30 --datadir=/usr/local/var/mysql --tmpdir=/tmp