Delete Users and Groups from Terminal on Mac

This Process can be Useful in situations like the followings:

• After the Installation of some Software like MySQL you can have some
  problem with the Automatically Created user.
• If you try to add an User or Group from System>Preferences
  and you find it already exists but this doesn't permit you to Login on a
  Terminal Session.

So you need to open a Terminal Session ( /Applications/Utilities/Terminal.app)

a) To Delete a User

dscl . -delete /Users/yourUserName

b) To Delete a Group

dscl . -delete /Groups/yourGroupName

After you are Free to Re-Create User and Group from System Preferences.

If You Re-Create User and Group by System Preferences after you Should Repair Ownerships on Directories and Files Owned by the Deleted Users/Groups.
For example if you deleted and recreated "mysql" User and "mysql" Group after you will need to Recursively set ownership by:

sudo chown -R mysql:mysql /usr/local/mysql

Extra Indications:

Mac HOW-TO Make a Command Alias 4 Easy-Quick Execution

The Guide Show How-to make a Command Alias as Time-Saver.