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Re: relational databases

From: wombat <wendy.cox2_at_ntlworld.com>
Date: 13 Feb 2003 06:31:49 -0800
Message-ID: <f12b00a0.0302130631.3ed7e545@posting.google.com>


Alan Gutierrez <ajglist_at_izzy.net> wrote in message news:<Pine.WNT.4.53.0302120843510.1332_at_CX1198465-B>...
> On Wed, 12 Feb 2003, wombat wrote:
>
> > I have a database assignment that seems to product a relation with one
> > composite primary key and no other attributes. It does not link two
> > relations, but just extends off of one. Is this legal? The relation
> > contains three attributes; ProductID, ProductName and ProductType.
> > The ProductType contains repeating groups and is not sustained by the
> > primary key (productid), so has been removed along with a copy of the
> > primary key to a new relation, but this creates a table with only a
> > primary key and no other relations. It does solve the problem of some
> > redundancy, but not much. Is this correct?
>
> Some redundancy? Just a little is annoying. Could you please post the
> DDL for the tables in question. It would make it much easier to
> visualize you problem.
>
> Alan Gutierrez - ajglist_at_izzy.net

In our assigment we have been given a snippet of sample data and told to normalise it to BCNF. The sample data is as follows:

ProductID ProdName ProdType PartNo PartCost AsNo AsName ToolID

101        Sink      Bthroom   123     25.78     4342  Olive   AB53
101        Sink      Bthroom   156     26.45     6543  Brown   ER34
105        Bath      Bthroom   156     26.45     2321  Green   TR34
105        Bath      Bthroom   178    101.23     6543  Brown   PO23
108        Stool     General   123     25.78     8767  Smith   QW12
108        Stool     General   164     32.00     OI98  Brown   YT45

When I come to the first normalisation stage of removing repeating groups, I end up with three relations:

PRODUCT (ProductID, ProductName) ProductID = primary key PRODUCTTYPE (ProductID, ProductType) ProductID, ProductType = primary key
PART (ProductID, PartNo, PartCost, AsNo, AsName, ToolID) ProductID,PartNo = primary key

Obviously, to get rid of further redundancy I have to finish the normalisation process.

As I am fairly new to this concept, I wasn't sure what you meant by DDL so I hope this explains it to you more clearly. Thanks for your help.

Wombat Received on Thu Feb 13 2003 - 08:31:49 CST

Original text of this message

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