Re: normalization question
Date: Mon, 27 Apr 2009 08:15:34 +0200
Message-ID: <gt3ihl$qq1$1_at_ss408.t-com.hr>
R(CustomerID, VendorID, ItemID, BoxID)
R is a key itself. So there are no non-prime attributes and R must enforce
#1, #2, #3 and BCNF.
Simpler is better!
Here are the rules:
The question is, how is this modeled in the highest possible normal
form.
So far I’ve come up with two possible solutions, both unsatisfactory:
Box Entity, which has a unique key of CustomerID, VendorID, and Date
BoxItem Entity, which has a unique key of BoxID, and ItemID
This solution does not enforces rule #3
Alternatively, I've come up with:
This does not comply with third normal form. What happens when the
ShipmentID/BoxID of a ShipmentItem does not match the ShipmentID of
the Box? It could be argued that this does not adequately enforce
rule #2
Any ideas on the “proper” way to model this? WWDACD (Would would Date
"myotheraccount" <levtoma_at_yahoo.com> wrote in message
news:4d142477-3b5d-4e56-a7de-34415d2bb728_at_u10g2000vbd.googlegroups.com...
I've run into a design issue that I just can't wrap my head around. I
tried to model here below with different types of information, as the
actual information I am modeling is confidential.
1) There are items, vendors, customers, and boxes.
2) Boxes contain items and are sent from one vendor to one customer on
a specific date.
3) Items can only be sent once from each vendor to each customer
Shipment Entity, which has a unique key of CustomerID and VendorID.
Box Entity, which has a unique key of ShipmentID and Date
ShipmentItem Entity, which has a unique key of ShipmentID and ItemID,
and contains a BoxID
Thanks in advance!
Received on Mon Apr 27 2009 - 08:15:34 CEST