Ian, Thanks for the reply.
I used ID as Key for and it works. But question is, can I use ID for all attributes (First, Last Name, Address etc...) to avoid duplicate error??? I think it's not correct way. That's why I gave option 2 as well.
Though we can fix those data issues in DB or using Named Query in DSV, I'm interested to know any performance issues while using Key Column properties.
Suresh