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Prime Attributes Expand / Collapse
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Posted Wednesday, October 12, 2011 11:26 AM
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Oops, mistook the word "every" for "any" in the candidate key answers.
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Posted Wednesday, October 12, 2011 11:31 AM


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

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Post #1189345
Posted Wednesday, October 12, 2011 11:42 AM


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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
Post #1189355
Posted Thursday, October 13, 2011 3:48 AM
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Thanks, now it's clear that my english has to be improved.
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Posted Thursday, October 13, 2011 3:56 AM


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Good question tom



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Posted Thursday, October 13, 2011 5:23 AM


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very good question!!!
thanks Tom!!



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Posted Thursday, October 13, 2011 5:45 AM
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You always submit tough questions. Thanks for making us think.

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Posted Thursday, October 13, 2011 7:54 AM


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Thanks for the question Tom.



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Posted Tuesday, October 25, 2011 11:43 PM


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Great question. You got me at "unique value for every row".



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