PLEASE help ME , HOW TO GENERATE PRIMARY Keys on the fly

Dear friends,

I have table

MD_CUSTOMER

MD_CUSTOMERIDPK integer primary key

NAME                           varchar

But my primary key is not in correct order like

MD_CUSTOMER

MD_CUSTOMERIDPK                     NAME

10                                                                                                                ANDI

33                                                                                                                TESTER

100                                                            KKK

, so I want to make other primary key to generate sequences 1, 2, 3, … and in MS SQL SERVER 2005

I can with Rank() function , but in Postgres how ?

PLEASE any one can help me, I am really appreciate.

Best regards

Andi kusnadi