Part (PartNum, Description, OnHand, Class, Warehouse, Price, (OrderNum, OrderDate, CustomerNum,...

Part ( PartNum, Description, OnHand, Class, Warehouse, Price,

(OrderNum, OrderDate, CustomerNum, CustomerName,

RepNum, LastName, FirstName,

NumOrdered,

QuotedPrice

)

)




NumOrdered,

QuotedPrice

)

)

This table is quite meaningful from the user point of view.

It describes the actual operation---as reflected by the database.




NumOrdered,

QuotedPrice

)

)

This table is quite meaningful from the user point of view.

It describes the actual operation---as reflected by the database.

But what if we have a part that has not been ordered yet?




NumOrdered,

QuotedPrice

)

)

In that case we need to work on the table and change it.

The structure should be such that update anomalies are not present.





NumOrdered,

QuotedPrice

)

)

Let’s determine functional dependencies.


PartNum determines: Description

OnHand

Class

WareHouse

Price




NumOrdered,

QuotedPrice

)

)

OrderNum determines: OrderDate

CustomerNum




NumOrdered,

QuotedPrice

)

)

CustomerNum determines:

CustomerName

RepNum




NumOrdered,

QuotedPrice

)

)


CustomerName

RepNum


(OrderNum, OrderDate, CustomerNum,

CustomerName,


NumOrdered,

QuotedPrice

)

)


CustomerName

RepNum which determines

LastName

FirstName



CustomerName,


NumOrdered,

QuotedPrice

)

)



CustomerName,

RepNum,

LastName,

FirstName,

NumOrdered,

QuotedPrice

)

)



CustomerName,

RepNum,

LastName,

FirstName,

NumOrdered,

QuotedPrice

)

)

There’s also (PartNum, OrderNum)



CustomerName,

RepNum,

LastName,

FirstName,

NumOrdered,

QuotedPrice

)

)

There’s also (PartNum, OrderNum) which determines

NumOrdered



CustomerName,

RepNum,

LastName,

FirstName,

NumOrdered,

QuotedPrice

)

)

There’s also (PartNum, OrderNum) which determines

NumOrdered and

QuotedPrice



CustomerName,

RepNum,

LastName,

FirstName,

NumOrdered,

QuotedPrice

)

)

So now what do we do?



CustomerName,

RepNum,

LastName,

FirstName,

NumOrdered,

QuotedPrice

)

)

1. Normalize the table (it has repeating groups).



CustomerName,

RepNum,

LastName,

FirstName,

NumOrdered,

QuotedPrice

)

)


2. Eliminate partial dependencies.



CustomerName,

RepNum,

LastName,

FirstName,

NumOrdered,

QuotedPrice

)

)



3. Make sure the only determinants are candidate keys.


OrderNum, OrderDate, CustomerNum,

CustomerName,

RepNum,

LastName,

FirstName,

NumOrdered,

QuotedPrice

)




Part ( PartNum,


CustomerName,

RepNum,

LastName,

FirstName,

NumOrdered,

QuotedPrice

)




Parts (PartNum, Description, OnHand, Class, Wartehouse, Price)

Part ( PartNum,


CustomerName,

RepNum,

LastName,

FirstName,

)

OrderLine (PartNum, OrderNum, NumOrdered, QuotedPrice)





Part ( PartNum,


CustomerName,

RepNum,

)

Rep (RepNum, LastName, FirstName)






Part ( PartNum,


)

Customer (CustomerNum, CustomerName, RepNum)







Part ( PartNum,


)








Orders (


)








Orders (OrderNum, OrderDate, CustomerNum )





Orders (OrderNum, OrderDate, CustomerNum )

End of story…





Second problem: (Henry Books Case Problem One)

Using the types of entities found in the Henry Books database (books, authors, publishers), create an example of a table that is in first normal form but not in second normal form and an example of a table that is in second normal form but not in third normal form. In each case, justify your answer…


This is an example about the power of assumptions.



Take this table:

(ISBN, AuthorSSN, AuthorName)



Take this table:


If we assume that a book can only have one author (that's pretty restrictive, but think about semester projects where group work is not allowed) then the above table is in 2NF already (ISBN is the key) but not in 3NF because of AuthorSSN being a non-key determinant (of whom?)



Take this table:


If we relax the requirement, and allow co-authors, then the table is no longerin 2NF. That's because we need to include the AuthorSSN column in the key and the functional dependency

(AuthorSSN AuthorName) becomes a partial dependency; it was about the existence of non-key determinants in the other context

Part (PartNum, Description, OnHand, Class, Warehouse, Price,



NumOrdered,

QuotedPrice

)

)

Part ( PartNum,

Description, OnHand, Class, Warehouse, Price,


CustomerName,

RepNum,

LastName,

FirstName,

NumOrdered,

QuotedPrice

)

Part ( PartNum,



CustomerName,

RepNum

NumOrdered,

QuotedPrice

)


Part ( PartNum,



CustomerName

NumOrdered,

QuotedPrice

)

Customer (CustomerName, RepNum)


Part ( PartNum,



NumOrdered,

QuotedPrice

)



Part ( PartNum,


OrderNum,

NumOrdered,

QuotedPrice

)

Orders (OrderNum, OrderDate, CustomerNum)



Part ( PartNum,

OrderNum,

NumOrdered,

QuotedPrice

)

Parts (PartNum, Description, OnHand, Class, Warehouse, Price)




OrderLine ( PartNum,

OrderNum,

NumOrdered,

QuotedPrice

)





OrderLine ( PartNum, OrderNum, NumOrdered, QuotedPrice)





Part (PartNum, Description, OnHand, Class, Warehouse, Price, (OrderNum, OrderDate, CustomerNum,...

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