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Re: Why spurious tuples with fifth normal form?

From: <stowellt_at_gmail.com>
Date: 16 Jun 2005 12:39:37 -0700
Message-ID: <1118950777.376315.19390@g49g2000cwa.googlegroups.com>


Good questions. Please correct me if I'm wrong, but isn't a join dependency when you are able to join decomposed tables on common keys to get the original table? In my case, I thought I had found a join dependency because most of the time, if I joined the decomposed tables together I got the original back. But every so often a spurious tuple showed up. Would this be an example of checking if a JD held? (and it didn't hold when the spurious tuple showed up)? Is the only way to check this by trial-and-error?

So if there would have been no spurious results, then I assume the JD would have held and thus I should have decomposed. I'm just not sure why my data set didn't have the JD when I have seen similar sets of data (with three inter-dependant columns) that did have JD's. Are all JD's cyclic? Thanks, I appreciate the explanations. Received on Thu Jun 16 2005 - 14:39:37 CDT

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