Someone ask me a question. Let's say we have following tables: tb_person(person_id, name, age, sex, location), tb_city(city_id, population, ..., name). tb_person.person_id points to tb_city.city_id. There are so many records in both tables. He seperate the tb_person into like: tb_person_in_shanghai, tb_person_in_Beijing, etc. He deleted location field to let the records to be less to improve the performance when query. I think that looks ugly. Do you think it's a right way or you have any other good idea?