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Thread: Drawing Entity relationship diagrams

  1. #1
    Join Date
    Oct 2013
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    Drawing Entity relationship diagrams

    Hi I am new here. I have to draw an erd, well I finished drawing it, just trying to figure out a few things. I'm not sure if this is the right place. Thanks.

  2. #2
    Join Date
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  3. #3
    Join Date
    Oct 2013
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    Draw the corresponding ERD for the following data structure:

    ERD First Draft.jpgProducts(ProID, Descrip, Cost, Price, CatID)
    People(ID, FName, LName, Phone)
    Clients(CID, CreditLimit)
    Employees(EID, DOH, DOB, SupervisorID)
    ClientAddress(CLID, CID, Street1, Street2, City, State, Zip)
    PriceHistory(PrID, ProductID, Price, StartDate, EndDate)
    InvDetail(InvNum, DetID, Qty, ProdID, UnitPrice, Discount)
    InvHeader(InvNum, Date, ClientID, CliAddrID, SalesPersonID, Memo)
    Categories(ID, Description)
    Underline stands for primary key
    Italic stands for Foreign key.

    I'm confused about the relationships. Any help will be greatly appreciated.

  4. #4
    Join Date
    Nov 2002
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    It is using crow-foot notation for relations between different entities. The crow foot side is many side in a relation. For example, a Product can have many PriceHistory records. One to one relation does not have any crow foot (you can draw an arrow), such as each Employee has one corresponding People record.

    In a foreign key relation, the child table inherits primary key of the parent table.

  5. #5
    Join Date
    Oct 2013
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    1
    Sorry to Hijack but could I get a little help with the entities and attributes on this one?

    AllCars wishes to create a system to monitor the rental of vehicles to clients. The company has various outlets and each outlet has staff including a Manager and a number of mechanics. Each outlet has a stock of vehicles for rent that may be rented by clients for various periods of time. Each rental agreement between the customer and AllCars is identified through a rental number. A client must take out insurance cover for each vehicle rental period and a vehicle is checked for faults after each rental.

    Thanks!

  6. #6
    Join Date
    Nov 2002
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    New Jersey, USA
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