I had a problem lately, while installing the development environment on my machine. I needed to install two different versions of MySQL. It seems brew has a way to manage multiple versions of a formula and switching between them just like we do with rvm and rubies. For this you need homebrew versions tap installed on your machine.
First switch to your local brew directory:
$ cd /usr/local
One you are in the brew directory, you can check the available
/usr/local$ brew versions mysql
5.6.20 git checkout 8f59be5 Library/Formula/mysql.rb
5.6.19 git checkout 3d3d8ae Library/Formula/mysql.rb
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In order to get a particular version, just checkout the matching commit.
/usr/local$ git checkout 336c976 Library/Formula/mysql.rb
This will checkout the specified version of the formula to the cellar. In order to install the other version, first we need to unlink the existing version of the forumla.
/usr/local$ brew unlink mysql
Unlinking /usr/local/Cellar/mysql/5.6.20... 14 symlinks removed
Now you can install the current cellar version of the formula.
/usr/local$ brew install mysql
Once the installation is complete, you can easily switch between the different versions of the formula.
/usr/local$ brew switch mysql 5.6.20
Cleaning /usr/local/Cellar/mysql/5.5.19
Cleaning /usr/local/Cellar/mysql/5.6.20
14 links created for /usr/local/Cellar/mysql/5.6.20