Hi,
i'm currently doing an auction site where there are two roles: Buyer and Bidder. In the system, the buyer cannot be the bidder and the bidder cannot be the buyer. If the buyer wants to be a bidder, he/she would need to register as bidder. And vice verse.

Registration details needed for bidder:
- username
- password
- emailaddress
- introduction (optional)
- websiteurl (optional)

Registration details needed for buyer:
- username
- password
- emailaddress


Quite some time ago, i've created two tables. One to store the bidder registration details and another to store the buyer details. I did it this way because i thought it would be much easier to manage the buyer and the bidder separately. But i realised that there are similar fields in both tables. I need some advice if i could continue my project this way or i have to do it the supertype/subtype way(i've to recode the application)? Will there be any major problems that are likely to happen in future if i were to continue using the tables this way? I would be glad if i could keep the structure this way. Please help.

What if the auction site decides to have third type of role? Will there be a third table for this ? Besides this, all constraints on buyers, almost all, will also be applicable to the bidders !
You can keep all the roles\registration info in one table. A flag can identify the role.