Re: Database Design Problem...

I agree with the other posts that say to keep the design as you have it with an exception. Instead of generating the ID as MAX+1, I would implement a sequence to generate the ID. If two people are entering a new book at the same time, it is possible to have duplicate ID's. Michael. Bret Halford wrote: > > 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