0 0 votes prime attributes are any attribute that are members of candidate key cant we say that members of SK are also prime attributes? Databases + – sudsho 2.1k views answer comment Share Follow Print 0 reply Please log in or register to add a comment.
Best answer 1 1 vote No its not true.. Suppose a relation R(ABCD) and let AB be the candidate key. Then the prime attributes are : A,B But superkey can be either of AB , ABC , ABD , ABCD So lets consider a superkey : ABC so C is also a member of ABC but C is not a prime attribute as C is not part of AB :) I hope u got the point. Habibkhan answered Oct 9, 2016 • selected Oct 9, 2016 by sudsho Habibkhan comment Share Follow See all 8 Comments 8 8 Comments reply Show 5 previous comments Habibkhan commented Oct 9, 2016 reply Follow flag Since there is a dependency AD --> B and for 3NF we require either AD is a key which is not the case nor B is a prime attribute .So it is not in 3NF. But since AD is not a proper subset of AC so it is in 2NF.Had it been a proper subset say C and it were derive a non prime attribute say B then it would be a partial dependency 1 1 replyShare sudsho commented Oct 9, 2016 reply Follow flag ohk thankyou :) 0 0 replyShare amolagrawal commented Dec 31, 2016 reply Follow flag Considering same example... Correct me if i my understanding is wrong. AC -> B is not a partial dependency since AC is not the proper subset of candidate key, it is a candidate key. Had it been C -> B or A -> B it would be partial dependency. Thanks in advance. 0 0 replyShare Please log in or register to add a comment.
1 1 vote No, we cant say that members of SK are also prime attributes? Set of all attribute is super key if you take prime attribute as any attribute that are members of Super key Then all attribute became prime attribute Shubham Pandey 2 answered Oct 9, 2016 Shubham Pandey 2 comment Share Follow See all 5 Comments 5 5 Comments reply sudsho commented Oct 9, 2016 reply Follow flag suppose AC is a CK A and C are then prime attributes and ACD is a SK so in ACD ..what we call A,C? 0 0 replyShare Shubham Pandey 2 commented Oct 9, 2016 reply Follow flag "suppose AC is a CK A and C are then prime attributes and ACD is a SK so in ACD ..what we call A,C? " then also AC is prime attribute but on the bases of AC ck we cant say anything on the bases of super key example R(ABC) in this relation A only is primary key , candidate key Super key is : A, AB, AC, ABC so here we can say that A is prime attribute but on the bases of candidate key 0 0 replyShare sudsho commented Oct 9, 2016 reply Follow flag ohk thnks...one more thing if suppose AC is a candidae key for any relation and we have a FD as AD->B then is this a transitive dependency? 0 0 replyShare Shubham Pandey 2 commented Oct 9, 2016 reply Follow flag No, https://en.wikipedia.org/wiki/Transitive_dependency 0 0 replyShare sudsho commented Oct 9, 2016 reply Follow flag then what is this? what will be the highest normal form for such relation? 0 0 replyShare Please log in or register to add a comment.
