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  1. #1
    Join Date
    Apr 2012
    Posts
    5

    er diagram for online book store

    I came across this question in a uni assignment of mine. Anyhow I found answers for it in the internet. But I cant understand some parts of it. This is the question.

    ABC Company needs to create and online book store to keep information about the books they sell. A customer can buy many books which can be identified by the year, title, price and the ISBN number. Each book can be written by one or many authors who’s name and addresses can be stored in the database as well. A particular book can be published by many publishers and their name, address, phone and web URL need to be stored in the database as well. A book will be stored in different warehouses which will have different quantities of books. Each warehouse can have a code, phone number and an address. System needs to store information about the customers such as their names, address, phone and email. Each customer can maintain different shopping baskets which can have a separate basket ID and each basket can contain many number of books.

    1. Construct the ER diagram which models the online bookstore.


    answer 1

    ImageShack® - Online Photo and Video Hosting

    in the above picture there are attributes called "number" attached to "contains" and "stores". what is mean by them ?

    I also need help with below questions
    should I add a entity calles "music item" and them connect them to 2 more entities called "cd" and "cassette".if so how to connect them with shopping basket ?

    2. Suppose the bookstore adds music cassettes and compact disks to its collection. The same music item may be present in cassette or compact disk format, with differing prices. Extend the E-R diagram to model this addition, ignoring the effect on shopping baskets.
    3. Now extend the E-R diagram, using generalization, to model the case where a shopping basket may contain any combination of books, music cassettes, or compact disks.

    thank you

  2. #2
    Join Date
    Apr 2012
    Posts
    5
    can someone please help me

  3. #3
    Join Date
    May 2008
    Posts
    277
    Quote Originally Posted by vpowerc View Post
    in the above picture there are attributes called "number" attached to "contains" and "stores". what is mean by them ?
    This is simply to record the quantity of an item in a shopping cart or warehouse.

    2. Suppose the bookstore adds music cassettes and compact disks to its collection. The same music item may be present in cassette or compact disk format, with differing prices. Extend the E-R diagram to model this addition, ignoring the effect on shopping baskets.
    3. Now extend the E-R diagram, using generalization, to model the case where a shopping basket may contain any combination of books, music cassettes, or compact disks.
    The assignment appears to be teaching you about supertyping/subtyping. Do some research into that to help with these last two questions.

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