Changing the primary key

[Ranetbauer, Michael]

Hi 
 
IŽ'm new with mysql and have following question:
 
I have a table, that has a primary key with two columns and want to add a
third column to this primary key.
 
Is this possible and when yes: Do I have to delete all tables, that
reference to this table?
 
Best regards
 
Michael R.