kangfend/homebrew_multiple_mysql_versions.md

Install the current version of mysql.

# Install current mysql version
brew install mysql

# Start agent for current version of mysql (including on login)
ln -sfv /usr/local/opt/mysql/*.plist ~/Library/LaunchAgents
launchctl load ~/Library/LaunchAgents/homebrew.mxcl.mysql.plist

Install the older version of mysql.

# Find older mysql versions
brew search mysql  
  
# Install older mysql version
brew install homebrew/versions/mysql56

# Start agent for older version of mysql (including on login)
ln -sfv /usr/local/opt/mysql56/*.plist ~/Library/LaunchAgents
launchctl load ~/Library/LaunchAgents/homebrew.mxcl.mysql56.plist

Then to switch to the older version.

# Unlink current mysql version
brew unlink mysql 

# Check older mysql version
ls /usr/local/Cellar/mysql56 # => 5.6.27

# Link the older version
brew switch mysql56 5.6.27

And to switch back to the current version.

# Unlink older mysql version
brew unlink mysql56 

# Check current mysql version
ls /usr/local/Cellar/mysql # => 5.7.10

# Link the current version
brew switch mysql 5.7.10

To verify which mysql version you're on at any time.

# Check which version of mysql is currently symlinked
ls -l /usr/local/bin/mysql

And if you only want only one version's agent running at a time (database agents/daemons can use a lot of resources).

# Stop agent for current version of mysql
launchctl unload ~/Library/LaunchAgents/homebrew.mxcl.mysql.plist
rm ~/Library/LaunchAgents/homebrew.mxcl.mysql.plist

# Stop agent for older version of mysql
launchctl unload ~/Library/LaunchAgents/homebrew.mxcl.mysql56.plist
rm ~/Library/LaunchAgents/homebrew.mxcl.mysql56.plist