Comparing multiple Mysql tables to find duplicates

Hello everyone, I am trying to write a function that would compare one table to a number of other tables in Mysql and remove any duplicates found. This is for tables of email addresses where I want to remove any dups found. Example: Master list - compare to list1, list2, list3, and so on and remove matches found from list1, list2, list3 etc. *not* from Master list. Does anyone know of any such beast before I set out to reinvent it? Thanks. Chris