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  1. #1
    Join Date
    Nov 2011
    Posts
    6

    Unanswered: Rating - calculate or save

    Hi,

    I'm developing a system where customers can rate Shops.
    the question is, in a shop profile, when i want to show the numbers of products she sells and the average rating it got, do i need to query the rating table each time and calculate the data each time or should i save a field in the Shop table - RatingAverage which is update each time the shop is rated by some one.
    The same question about the number of sells - save a counter that update each purchase - or query the deals (count the numbers of deals with the specific shop)?

    which way is better?

    thank's a lot

    Amit

  2. #2
    Join Date
    Nov 2011
    Posts
    6

    help..

    some one please?

  3. #3
    Join Date
    Nov 2004
    Posts
    1,427
    Provided Answers: 4
    It depends.

    When your site gets a lot of hits, you may want to speed these things up by storing those values in denormalised columns. Especially when you have a lot more reads than writes.

    Denormalisation comes at a price, you must make sure those columns always contain the right values. But you could also take a more relaxed way, like saying: I will recalculate those values only every hour, or 15 minutes or so.
    With kind regards . . . . . SQL Server 2000/2005/2012
    Wim

    Grabel's Law: 2 is not equal to 3 -- not even for very large values of 2.
    Pat Phelan's Law: 2 very definitely CAN equal 3 -- in at least two programming languages

  4. #4
    Join Date
    Nov 2011
    Posts
    6

    thank you very much

    you helped me

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