Haskell String Comparison function

I'm having trouble writing a string comparison function for haskell. I have a text file and I need to compare 100+ first and last names from a text file

Amy, Patterson 
John, Doh

in that format. I know that I need something to compare ">" greater than or "<" less than for comparison... The comparison function's result will be fed into a sorting algorithm (if this info matters).

Given my beginner status, I would like some help if possible. Thanks!