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  1. #1
    Join Date
    Feb 2009
    Posts
    4

    ER Diagram n00b help

    just sorta starting working on basic Database design etc.. Unfortunately the book isn't laid out very nice and jumps around quite a bit.. nevertheless trying to set up a ERD.

    so per say I had 3 entity sets.. (Televisions, Manufacturer and Shop)

    obviously TV's would have a manufacturer and a shop that sells them.. but you can't be a shop and manufacturer.

    If the manufacturer sells to a Shop.. then the some of the info would be stored.. (date, product etc..) I believe this is where the inheritance comes in that's throwing me off.

    thanx for any help

  2. #2
    Join Date
    Jun 2007
    Location
    London
    Posts
    2,527
    thanx for any help
    Traditionally with homework assignments your supposed to give your best effort at a design (a list of tables and fields is fine) and then we comment where you might of made any mistakes. You're unlikely to learn much by just asking for a solution.

  3. #3
    Join Date
    Feb 2009
    Posts
    4
    Quote Originally Posted by mike_bike_kite
    Traditionally with homework assignments your supposed to give your best effort at a design (a list of tables and fields is fine) and then we comment where you might of made any mistakes. You're unlikely to learn much by just asking for a solution.
    I listed approx 1/10 of the assignment and specifically asked on how inheritance would be done. We did learn conversion from ERD to tables just a day or two ago though.. so unsure of how that might come out. All done anyways.. thanx for the help..

  4. #4
    Join Date
    Apr 2002
    Location
    Toronto, Canada
    Posts
    20,002
    the closest you get to inheritance in ERDs is with the supertype/subtype structure
    rudy.ca | @rudydotca
    Buy my SitePoint book: Simply SQL

  5. #5
    Join Date
    Sep 2002
    Location
    UK
    Posts
    5,171
    Here's an article that show's an example of supertype/subtype in an ERD.

  6. #6
    Join Date
    Apr 2002
    Location
    Toronto, Canada
    Posts
    20,002
    have a look at this, there are some really excellent examples:

    Supertypes and Subtypes PPT (unfortunately with annoying transition sounds)
    rudy.ca | @rudydotca
    Buy my SitePoint book: Simply SQL

  7. #7
    Join Date
    Feb 2009
    Posts
    4
    wanted to thank everyone for the links. I want to have a good general understanding of database design etc..

    IMO my text book is extremely poorly written vs. almost any other text book I've ever had.

    we've moved from ERD's to Table Schemas to Relational algebra & quieries in a mere weak.. so I might invest in a more well written book over the weekend.

    thanks.

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