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  1. #1
    Join Date
    Oct 2007
    Posts
    13

    Dont know if this is an entity

    Hi, looking for some help here, I have a uni project to design a database for the uni library that supplies textboooks for students, these textbooks are orderd from a booklist given by course lectures, a booklist is given for each unit they take. Also the library sells books to the general public and orders books for them. This is my problem,

    Is Textbook, Booklist and Book, different entities (We havent to use inheritence in this project), If I use them as different entities then the order entity will be all over the place, any help would be great thanks, Im just of to a lecture but will check back in when I get back, hope someone can help

  2. #2
    Join Date
    Feb 2004
    Location
    In front of the computer
    Posts
    15,579
    The simple test to determine if something is an entity is if you can imagine it as a discrete object. I can imagine a Textbook, Booklist, and a Book so I'd say that they were entities.

    The simple test to determine if one entity is a "child entity" of a different entity is if one entity has all of the common attributes and no other attributes... If so, that entity is a candidate for being a parent entity. In your example, I'd guess that one of the entities might be a parent entity.

    -PatP

  3. #3
    Join Date
    Oct 2007
    Posts
    13
    Thaks mate, I have choosen my entites for days now, but keep getting hung up on it, I should just stick with them and see what happens, time is running out due in next week.

    Cheers

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