Database Normalization

Normalize to 3NF and BCNF

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2 Replies - 1434 Views - Last Post: 04 November 2010 - 05:35 PM Rate Topic: -----

#1 nquadr  Icon User is offline

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Database Normalization

Posted 31 October 2010 - 12:31 PM

My task is to normalize this table into 3NF and then BCNF.

So far I have done what is in my attachments. But my professor said the functional dependencies that I have are different than his.

His dependencies can be found in table 1NF (2). I need to find out why his method is right versus my method. I cannot rationalize it in my head.

If you can help, it would be great.

It seems that I cannot post an excel file. So he has chosen
SSN --> LName, Major, Advisor
CrsName --> CrsNo, Credits
as his tables that have functional


dependencyAttached File  Assignment2-1.doc (240K)
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Replies To: Database Normalization

#2 andy_pleasants  Icon User is offline

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Re: Database Normalization

Posted 03 November 2010 - 02:17 AM

Basically we'll take the first table:

SSN --> LName, Major, Advisor

This is a functional dependency (or to phrase it better the values (LName, Major, Advisor) all have a functional dependency on the key (SSN)) We can verify this by saying this:

If I give you a SSn, will you be able to give me 1 UNIQUE set of values (LName, Major and Advisor) with no ambiguity? Yes you will. This means that the values are functionally dependent on the key or

X -> Y

Where X = primary key (SSN)
and Y are the values (LName, Major, Advisor)

The same can be applied to his other table as well.

Now your table, if I was to give you a SSN, would you be able to give me one, unambiguous row? No, because you can see that for some SSNs there is more than on CrsCode! This is not a functional dependency, understand?
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#3 andy_pleasants  Icon User is offline

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Re: Database Normalization

Posted 04 November 2010 - 05:35 PM

Also, just to take this one step further (since this is a place to share knowledge).

Ensuring all the records in a table have a functional dependency on the key means that you can perform "identification" on the set of data. This means operations such as add, edit, delete and retrieve (basically the CRUD operations) can be performed without ambiguity.
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