Hi Selvam,
what do you mean, like in ECC? You mean in SD customer? There you also do not derive from partner function but from Account group. You can think account groups as mirror object of business partner grouping in this case.
Please, don't be confused by the naming - in SD standard, there is account group 0001 called Sold-to party and also partner function called Sold-to party. When you createte customer in ECC, then you must select account group, partner functions can be added/modified later. You can have more partner functions per customer but only one account group by customer.
The same is in CRM with business partner and business partner group and roles.
Regards,
Dawood.