Re: Database Design Problem...

Jimmy wrote: > > Hello all, > > I have a databases design problem. > Recently, I want to implement a table which stores information about > books. > So I decide to create the table BOOK with the following attributes: > > book_id number, > book_name char(10), > author char(30)... > > book_id is a primary key and is automatically generated by the system. > (max + 1) > Then another table, ORDER, which is used to store the inforamtion about > the order. One of the attributes of this table is book_id, which is a > foreign key and related with the book_id of the table BOOK. > I think the design is OK. > However, one day, a person ask me, "Why you put book_id in the table > BOOK? book_name is unique all the time, why you create additional column > (book_id) in table BOOK? Moreover, I don't know which book is from the > table ORDER since it contains book_id only. book_id is meaningless. Why > don't you delete the book_id column in table BOOK and replace book_id > with book_name in table ORDER?" > > I think create the ID column for the book (or other table) is common in > the relational database. Although the book name is unique, create an ID > column is much easier to manipulate. Am I right? Or should I delete the > ID column? Any comment will be appreicated. > Your friend is mistaken, book titles are >NOT< unique. While publishers usually try to avoid duplicate titles, they can and do happen. An example: Both Jackie Koller and John Tanner have authored books titled "The Falcon". Furthermore, a book_id can be used to differentiate different editions (version, paperback vs hardcover, book-club edition, etc) of the same book. Your schema also seems to be assuming that each book has a single author, which just isn't so in real life. The book "Physical Database Design for Sybase SQL Server", for instance, has three: Rob Gillette, Dean Muench, and Jean Tabaka. You might want to have a look at the "pubs2" sample database that comes with SQL Server. While it is not the ultimate design for a publisher's/bookseller's database, it is a pretty good start. -- Bret Halford Imagine my disappointment Sybase Technical Support in learning the true nature 3665 Discovery Drive of rec.humor.oracle... Boulder, CO 80303