1. Registered User
Join Date
Oct 2008
Posts
5

## non redundant covers

Hi,

Does anybody have some theoretical idea about functional dependencies.

I have to find non redundant covers and convert a relation to BCNF. But i am unable to understand the concept.

My question is:

Consider the following relations and the set of Function Dependencies(FDs):
SHIPMENT (ship_id, S_capacity, S_date, cargo, amount)
FDs are as follows:
Ship_id -->S_capacity
Ship_id, S_date --> cargo
Cargo, S_capacity --> amount

Now perform the following:
(i) Identify the key of the relation.
(ii) Find the non-redundant cover of the given FDs.
(iii) Normalize the relation into BCNF. Is the decomposition dependency preserving? Give reason for your answer.

Anyone who can help me out??????

2. SQL Consultant
Join Date
Apr 2002
Location
Posts
20,002
homework!!!

3. www.gvee.co.uk
Join Date
Jan 2007
Location
UK
Posts
11,445
What Rudy means is - we aint doing it for you!
Do the assignment as best as you can and you can ask for critique here.

4. World Class Flame Warrior
Join Date
Jun 2003
Location
Ohio
Posts
12,595
Originally Posted by mayurgogia
Does anybody have some theoretical idea about functional dependencies.
Sure. This guy has nothing but theoretical ideas about functional dependencies: http://www.dbforums.com/showthread.php?t=1633864

5. Registered User
Join Date
Oct 2008
Posts
5
Yes... Thanks all....
Finally I found it myself...... though it was difficult to understand from books...
(i) Key for the relation is (ship_id,s_date) because there does not exist any dependency as R-->key for key being a proper subset of R+. and all attributes are dependent on the key.
(ii) None of the given dependencies is redundant. So, non redundant cover for the dependency set is (Ship_id -->S_capacity;Ship_id, S_date --> cargo;Cargo, S_capacity --> amount)
(iii)Converting to the BCNF gives the following three relations for breakup of the given one:
shipment1(Ship_id,S_capacity);
shipment2(ship_id,s_date);
shipment2(ship_id,Cargo,amount)

#### Posting Permissions

• You may not post new threads
• You may not post replies
• You may not post attachments
• You may not edit your posts
•