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Thread: help anyone?

  1. #1
    Join Date
    Oct 2003

    help anyone?

    hey, i was wondering if anyone could tell me the benefits and drawbacks of denormalisation? and the types of cadidates for this process? i would appreciate it hugely if someone had any ideas, cheers

  2. #2
    Join Date
    Apr 2002
    Toronto, Canada
    as the saying goes, "when is this assignment due?"

    normalization usually reduces the overall size of the database (advantage), greatly simplifies updates (advantage), ensures data integrity (huge advantage), and may mean slightly slower select queries (disadvantage)

    denormalization is the exact opposite

    types of candidates for denormalization? data warehouses or data marts featuring summarized, temporal data, where codes and keys have been translated into human-understandable descriptions


  3. #3
    Join Date
    Jan 2003
    Duncan BC Canada
    and may mean slightly slower select queries (disadvantage)
    It may also mean faster select queries, depending upon how much redundancy is in the non-normalized form your comparing it to.

  4. #4
    Join Date
    Nov 2003
    Bangalore, INDIA

    Thumbs up


    Denormalisation is the act of having a single table containing all the informations regarding something. It results in Data redudancy, Data non-availability, No Data accuracy etc., In other words, data in an incosistent state.

    Data normalization is the act of breaking down column data to
    place in tables where each column in the table is functionally
    dependent on only one primary key. This process reduces data
    storage costs by eliminating redundancy and minimizes
    dependency of any column in the "normalized" database to only
    one primary key.

  5. #5
    Join Date
    Nov 2003
    Currently New York; Usually UK
    My take is that denormalization is a process or decision that occurs AFTER normalization, where for practical or performances reasons you make a conscious decision to break a normalization rule.

    So to begin with, your data structure is unnormal. Then you normalize it. Then you may make a decision to denormalize some part of it.

    Of course, all these processes could take place within a very short time of each other, or even may occur pretty much simultaneously.

    You may even decide on reflection that something has not been fully normalized, but justify this state for practical or performance reasons.

    You could also think of denormalizing as flattening out the data structure, typcially for exporting data to another system, though this is not necessarily an example that involves tables in this state, just the process that produces the export file.

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