Hi

I am studying an IT course and thought I was just beginning to master
the basics of normalization. However I came across an example in my
text book that wasnt what I would have arrived at.

It was the structure for a transactional database which allowed several
items to be purchased in a single order.

The text book suggested (Primary Key in capitals):

tblCustomer (CUSTOMER_NUMBER, Title, Surname, Forename, Initials,
Address1, etc)
tblOrder (ORDER_NUMBER, Part_Number, Quantity, Customer_Number, Date)
tblProduct (PART_NUMBER, Description, category, Price, No_in_stock,
Re_order_level, etc)
tblOrderLine (Order_Number, Part_Number, Customer_Number)

By myself I would have thought of:

tblCustomer (CUSTOMER_NUMBER, Title, Surname, Forename, Initials,
Address1, etc)
tblOrder (ORDER_NUMBER, Customer_Number, Date)
tblProduct (PART_NUMBER, Description, category, Price, No_in_stock,
Re_order_level, etc)
tblOrderLine (Order_Number, Part_Number, Quantity)

What am I missing?

Thanks

On Sun, 04 Jun 2006 07:52:34 -0700, smitj2 (AT) tiscali (DOT) co.uk wrote:

An error in the text book.

The inclusion of Part_Number in tblOrder is the error. Orders don't
have part numbers.

The inclusion of quantity is unusual, but might be valid. For example,
in a poorly conceived system it could be used as a quick check when the
order is shipped.

HTH
Jerry

smitj2 (AT) tiscali (DOT) co.uk wrote:
With that table design, you can only buy one type of part per order.

Yours looks better, but maybe there's something missing in the
requirements. You never gave the problem design requirements.

ed