Professional Web Applications Themes

Working Definition of 3rd Normal form - Microsoft SQL / MS SQL Server

Since every job interview I go toasks about all 3 normal forms all at once the definition like A database in third normal form has no repeating fields and groups in any record and only relevant, atomic keys. I know the use of the word 'atomic' may seem out of place, but who doesn't use the acronym ACID for transactions and the XML Schema specification uses 'particles' to quantify key relationships. "Second normal form is violated when a non-key field is a fact about a subset of a key." William Kent 1982 Is there something wrong with this definition? Does ...

  1. #1

    Default Working Definition of 3rd Normal form

    Since every job interview I go toasks about all 3 normal forms all at once
    the
    definition like
    A database in third normal form has no repeating
    fields and groups in any record and only relevant, atomic keys.

    I know the use of the word 'atomic' may seem out of place, but who doesn't
    use the acronym ACID for transactions and the XML Schema specification uses
    'particles' to quantify key relationships.

    "Second normal form is violated when a non-key field is a fact about a
    subset of a key." William Kent 1982

    Is there something wrong with this definition? Does it make sense to
    shorten it to 20 words?


    Jay Schmitendorf Guest

  2. #2

    Default Re: Working Definition of 3rd Normal form

    Your one sentence definition doesn't say enough about keys. What's a
    "relevant" key?

    1NF All attributes are atomic. There are no repeating groups.
    2NF Every attribute is functionally dependent on every part of the key.
    3NF There are no transitive (non-key) dependencies.

    In an interview situation, impress them by dropping in a mention of
    Boyce-Codd, 4th and 5th NF as well.

    --
    David Portas
    ------------
    Please reply only to the newsgroup
    --



    David Portas Guest

  3. #3

    Default Re: Working Definition of 3rd Normal form

    On this topic, can anybody suggest some good reading material that goes
    in-depth regarding NFs?

    Brad

    "David Portas" <REMOVE_BEFORE_REPLYING_dportasacm.org> wrote in message
    news:OVJXjELSDHA.2008TK2MSFTNGP11.phx.gbl...
    > Your one sentence definition doesn't say enough about keys. What's a
    > "relevant" key?
    >
    > 1NF - All attributes are atomic. There are no repeating groups.
    > 2NF - Every attribute is functionally dependent on every part of the key.
    > 3NF - There are no transitive (non-key) dependencies.
    >
    > In an interview situation, impress them by dropping in a mention of
    > Boyce-Codd, 4th and 5th NF as well.
    >
    > --
    > David Portas
    > ------------
    > Please reply only to the newsgroup
    > --
    >
    >
    >

    Brad M. Guest

  4. #4

    Default Re: Working Definition of 3rd Normal form

    I still like Chris Date's version to the efect that 3NF means that
    "all non-keys are determined by the key, the whole key and nothing but
    the key, so help me Codd!"
    --CELKO-- Guest

  5. #5

    Default Re: Working Definition of 3rd Normal form

    >> ... suggest some good reading material that goes
    in-depth regarding NFs? <<

    THEORY OF RELATIONAL DATABASES by David Maier; a math book that is
    unfortunately out of print.

    --CELKO--
    ===========================
    Please post DDL, so that people do not have to guess what the keys,
    constraints, Declarative Referential Integrity, datatypes, etc. in your
    schema are.

    *** Sent via Developersdex http://www.developersdex.com ***
    Don't just participate in USENET...get rewarded for it!
    Joe Guest

  6. #6

    Default Re: Working Definition of 3rd Normal form - Tossing relevant from definition

    You are right. Thanks for the coment and the advice. Mr. Codd's comment
    will work great in most places too, certainly day to day.

    That problem solved, this is to answer your question about 'What is a
    relevant key'.

    'Relevant key' came from trying to reduce 'Functionally Dependent.'
    'relevant' as in related to the problem domain, or meaningful, yet normal to
    the facts in our data model.
    Relevant to reaching a goal.

    The definition got me out of some murky water, avoided the question:
    Which functions?
    We want the definition to give us solid ground for excluding
    attributes produced by computation and deduction functions.

    That is probably because I over use normalization as a mechanical technique
    for brainstorming. I am usually adding attributes to the data model to get
    a reasonable or controllable approximation function for the behavior of a
    real thing. So 'relevant' was to qualify the function as being in the
    problem domain. Thanks to your reemphasis, I believe that the functions
    are the set of all reading functions. Maybe it is the list of functions
    where you already have the bigger concept. The 'what' part of the
    solution to the business problem has already been defined when normalization
    starts, so there is no reason to mention meaning.

    The reason for calling keys atomic was:
    a: atoms are not transient
    b: they are too small to contain a classification code

    Thanks again

    "David Portas" <org> wrote in message
    news:phx.gbl... 


    Jay Guest

  7. #7

    Default Re: Working Definition of 3rd Normal form

    >> On this topic, can anybody suggest some good reading material that goes
    in-depth regarding NFs? <<

    Regarding 1NF get the most recent article by Chris Date from dbdebunk.com.

    About 2NF & 3NF, you can get the info from most basic database text books.
    For simple details and examples, you can use the one by Korth &
    Silberschatz. For BCNF & higher normal forms up to 5NF you can refer to
    Introduction to Database systems by Chris Date or the book by Fleming & Von
    Halle

    For 6NF, read Temporal Data & Relational model by Chris Date. Also for a
    summary by Hugh Darwen, go through the website thethirdmanifesto.com

    --
    - Anith
    ( Please reply to newsgroups only )


    Anith Guest

Similar Threads

  1. breaking 1st Normal Form - Design Question
    By roch77@gmail.com in forum MySQL
    Replies: 0
    Last Post: July 24th, 03:25 PM
  2. (Repost) SQL Query Against Normal Form Tables
    By bcr07548@creighton.edu in forum MySQL
    Replies: 0
    Last Post: January 6th, 08:21 PM
  3. Form Not Working
    By VTKGS in forum Web Design
    Replies: 1
    Last Post: July 30th, 01:55 PM
  4. Form authentication, what about normal login?
    By Henry in forum ASP.NET Security
    Replies: 1
    Last Post: February 1st, 05:42 AM
  5. Form not working either
    By Mblom in forum Web Design
    Replies: 1
    Last Post: January 5th, 06:05 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139