Prime Attributes

  • Comments posted to this topic are about the item Prime Attributes

    Tom

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  • Great question Tom, I can say that as I surprised myself by getting the right answer 😀

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  • It is very good question. I was sure about the half part. Got to revise lots of things.

    Basics matter!!

    Best Regards,

    Sudhir

  • Darn! I don't know why, but I checked "has a different value on each row".

    Nice question, Tom.

    -- Gianluca Sartori

  • Hmmmm.

    I used the same source (http://en.wikipedia.org/wiki/Database_normalization) i hope (because the link provided on the result page isn't existing), and there is a definition: A prime attribute, conversely, is an attribute that does occur in any candidate key.

    But is it wrong then?

  • Thanks Tom. (open up QotD and knew immediately who wrote it! 😛 )

    After your question last week I did some revision so was a little better prepared to tackle this one today. Certainly making me flex the ol' brain in areas that are not as regularly flexed! 🙂

  • palotaiarpad (10/12/2011)


    Hmmmm.

    I used the same source (http://en.wikipedia.org/wiki/Database_normalization) i hope (because the link provided on the result page isn't existing), and there is a definition: A prime attribute, conversely, is an attribute that does occur in any candidate key.

    But is it wrong then?

    The context here is that Non-Prime attribute does not occur in any candidate key, so CONVERSELY, a PRIME attribute does occur in any [but not all] candidate keys

    The statement is correct, however the WIKI definition could certainly be worded a little better...

  • Too bad half right doesn't count for anything...

    Good question, Tom!

    Rob Schripsema
    Propack, Inc.

  • Nice question. Took much too long to shake the cobwebs out of my brain.

    If everything seems to be going well, you have obviously overlooked something.

    Ron

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  • Oops, mistook the word "every" for "any" in the candidate key answers.

  • Thanks for the question Tom. Your questions always make my brain hurt.

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  • palotaiarpad (10/12/2011)


    Hmmmm.

    I used the same source (http://en.wikipedia.org/wiki/Database_normalization) i hope (because the link provided on the result page isn't existing), and there is a definition: A prime attribute, conversely, is an attribute that does occur in any candidate key.

    But is it wrong then?

    Not the same page, but one just as good; I'm not sure what happened to that reference, it was cut and paste from my browser address bar. The definition on the wikipedia page you found contained a strange use of "any": "any" meaning "some". This is sort of logical but is a very unusual usage, so people get confused when "any" is used like that, and sometimes think it means "every". That wikipedia page has now been corrected and uses "some" instead of "any" which should be clearer.

    The writer of the original definition on the wikipedia page can be excused because he probably though that misinterpretation of that "any" would be avoided by that little word "conversely", which is saying that "prime" is the converse of "non-prime" which is defined immediately above (and the converse of "it isn't in any candidate key" is "it is in some candidate key") but it's better to avoid unusual usage and aim for clarity in something like wikipedia.

    Tom

  • Thanks, now it's clear that my english has to be improved. 😀

  • Good question tom

    Thanks
    Vinay Kumar
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