While writing a Power Search module for my accounting/customer management software, I came up with a great way to order results in MySQL.

The problem was this: some of our accounts are listed under a business name, and some are listed under a person's name.  You couldn't order by `BusinessName`,`LastName` because all the accounts that didn't have a business name listed would appear first in the list.  If you reversed it, all the accounts who had only a business name would appear first in the list.  The solution, fortunately, was beyond simple:

order by CONCAT(`BusinessName`,`LastName`,`FirstName`)

This is equivalent to saying "Sort by BusinessName, if it doesn't exist then sort by LastName, if it doesn't exist then sort by FirstName.  Yay!