[otrs] Customer table - UserLogin, email, Customerid

Hi! I try to use otrs within my support group - but I don't want to have UserLogin, email and Customerid as requiered fields, as not every Customer needs a login, not every Customer has an email address. I only need the id as primary key in the table (and that should be Auto Increment) Is there a way to do that, or at least to set automatic random default values for the fields? lg Maritn