In this paper we present a new rough sets model based on database systems. We borrow the main ideas of the original rough sets theory and redefine them based on the database theory to take advantage of the very efficient set-oriented database operation. We present a new set of algorithms to calculate core, reduct based on our new database based rough set model. Almost all the operations used in generating core, reduct in our model can be performed using the database set operations such as Count, Projection. Our new rough sets model is designed based on database set operations, compared with the traditional rough set models, ours is very efficient and scalable.