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  1. #1
    Join Date
    May 2008
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    9

    Unanswered: Normalising data

    Im a little stuck on normalising data and this is how far i got:

    Un-normalised data

    ID, Date-Time of bid, Bidders, Password, Design Code, Bid Amount, Bid Currently Successful, Last Name, First name, Title, Address Line 1, Town, County, Post Code, Telephone Number, Description, Reserve Price, Min Successful Bid

    1NF

    Bidders details: ID, Last Name, First name, Title, Address Line 1, Town, County, Post Code, Telephone Number,


    Date-Time of bid, Bidders, Password, Design Code, Bid Amount, Bid Currently Successful, Description, Reserve Price, Min Successful Bid

    what else could i seperate?

  2. #2
    Join Date
    Apr 2002
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    could we see the exact homework question please?

    it often helps to understand why the normalization is being done, and what sort of emphasis the various application processing requirements have on the overall collection of data items
    rudy.ca | @rudydotca
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  3. #3
    Join Date
    May 2008
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    9
    All it ask is to:

    Q) Use data modelling techniques to design an efficient database structure that minimises duplication of data.

    They also provide a little storyline thing which says in quick terms:

    Auctioning different plots.
    Bidders will apply for userID and pasword.
    57 plots with 8 different types of house.
    plots are about same, bidders will bidding for the housing type.
    When the auction is closed the Auction manager allocates the plots to the highest bidders for that housing type.
    Notification will be send detailing the plot number they have been allocated.
    Bidders can sign onto bidding system when they recieved their userIDs.
    They can then choose which housing type they require.
    The userID and password will be taken to the bidding screen
    They can then choose which housing type they require

  4. #4
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    Apr 2002
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    Toronto, Canada
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    okay, thanks, that's perfect

    quite the challenge, isn't it

    so, what are you looking at after bidders? can we see your next attempt?

    btw, password probably belongs with bidders, don't you think?
    rudy.ca | @rudydotca
    Buy my SitePoint book: Simply SQL

  5. #5
    Join Date
    May 2008
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    9
    i did think that but here is what i got:

    Un-normalised data

    ID, Date-Time of bid, Bidders, Password, Design Code, Bid Amount, Bid Currently Successful, Last Name, First name, Title, Address Line 1, Town, County, Post Code, Telephone Number, Description, Reserve Price, Min Successful Bid

    1NF

    Bidders details: ID, Last Name, First name, Title, Address Line 1, Town, County, Post Code, Telephone Number,


    Date-Time of bid, Bidders, Password, Design Code, Bid Amount, Bid Currently Successful, Description, Reserve Price, Min Successful Bid

    2NF

    Bidders details: ID, Last Name, First name, Title, Address Line 1, Town, County, Post Code, Telephone Number,

    Bids: Bidders, Password, Design Code, Bid Amount, Description, (maybe date-time of bid)

    Date-Time of bid, Bid Currently Successful, Reserve Price, Min Successful Bid

    3NF

    Bidders details: ID, Last Name, First name, Title, Address Line 1, Town, County, Post Code, Telephone Number,

    Bids: Bidders, Password, Design Code, Bid Amount, Description, (maybe date-time of bid)

    Plot: Date-Time of bid, Bid Currently Successful, Reserve Price, Min Successful Bid

    would you say this is correct?

  6. #6
    Join Date
    Nov 2004
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    out on a limb
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    Provided Answers: 59
    erm in short NO.. its getting there, but its not there yet
    why would you want to store a password in the bids table, unless you are using some form of unique password per bid.. surely a password 'belongs' to a bidder.

    why do you store the time of bid on a plot.. surely thats a function of the bid
    the reserve price.. Ok i understand that.. bid successful? what is that? agina thats an attrivute of a bid not a plot.

    I think you need to revisit the texts on normalisation, try this

    if it helpts try ot think of things as discrete data stores, what is an attribute of something.

    fer instance
    a person, has a title, forenames, surname, initials, qualifications, address, phone, email etc.

    however for certain circumstances there may be multiple addresses for a person

    a person can be both a bidder and a seller, mind you a compnay could be a bidder or a seller.

    I think most practitioners appearing on here are not going to be overtly familiar with the process of going from First to Third Normal forms and beyiond.. primarily thats not the way they tend to work. usually they can 'see' the data model at or near 3NF without having to go through the paper steps.

    Personally I try to think of the attributes of a model as belonging to an entity.. if there is no clear single candidate to associate an attribute with an entity then you may need to create a new entity. If you read the piece by Paul Litwin then it should become a bit clearer.
    I'd rather be riding on the Tiger 800 or the Norton

  7. #7
    Join Date
    May 2008
    Posts
    9
    The reason i left password into the bids was because the next question asked me to create a form and enter some bids detail in. But your correct about the others

  8. #8
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    Nov 2002
    Location
    Jersey
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    It's not that hard

    Just think of "things" as containers.

    Put all things that belong to a container, in that container

    If you are a bidder, do you yourself have a password, or does every bid have a password?

    Simple stuff really

    Do tires belong to a car, or the driver?

    The car would belong to the driver, the tires belong to the car, the type of tread belongs to the tire...

    get it?
    Brett
    8-)

    It's a Great Day for America everybody!

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    The physical order of data in a database has no meaning.

  9. #9
    Join Date
    May 2008
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    9
    ok thxz getting the picture now

  10. #10
    Join Date
    Nov 2002
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    Jersey
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    Quote Originally Posted by mackie01
    The reason i left password into the bids was because the next question asked me to create a form and enter some bids detail in. But your correct about the others

    Oh, and NEVER fall into this trap

    Having the application design, form the data model

    Many bad things happen this way

    A solid data model forces the app design to be correct...in spite of the developers
    Brett
    8-)

    It's a Great Day for America everybody!

    dbforums Yak CorralRadio 'Rita
    dbForums Member List
    I'm Good Once as I ever was

    The physical order of data in a database has no meaning.

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