2 votes 2 votes The number of partial dependencies in a relation R{X,Y,V,U,Z} with FD set F={X->YZ, Z->V, V->XY} is ____ Databases databases database-normalization + – ayushigupta asked Mar 2, 2017 ayushigupta 3.0k views answer comment Share Follow See 1 comment See all 1 1 comment reply Harsh Kumar commented Jul 11, 2018 reply Follow Share A functional dependency X → Y is a partial dependency if some attribute A ε X can be removed from X and the dependency still holds; that is, for some A ε X,(X – {A}) → Y. Nowhere in the question it is asked about the partial dependencies On CANDIDATE KEYS, so why the answers are based on this assumption..?? I think there are NO functional dependencies because you cannot remove any attribute from LHS..! 0 votes 0 votes Please log in or register to add a comment.
Best answer 3 votes 3 votes Candidate keys are XU,VU,ZU. So prime attributes= X,U,Z,V and non prime attributes= Y. Partial dependency means that a non prime attribute is functionally dependent on part of a candidate key. (A non prime attribute is an attribute that's not part of any candidate key.) In the dependencies non prime attribute Y is dependent on X which is part of candidate key XU. So X->YZ is a partial dependency. Similarly Y is dependent on V which is part of candidate key VU. So,there exists 2 partial dependencies which are X->YZ and V->XY. Arnabi answered Mar 2, 2017 • selected Oct 30, 2017 by Arnabi Arnabi comment Share Follow See all 2 Comments See all 2 2 Comments reply Tanmay Garg commented Mar 3, 2017 reply Follow Share X->YZ and V->XY themselves are not partial dependencies, but X->Y and V->Y (which can be implied from F) are partial dependencies. Hence, we can say that the set F has 2 partial dependencies. 1 votes 1 votes ankit commented Mar 3, 2017 reply Follow Share z--->y can also be derive from the above given FDs.. and z is the proper subset of zu and y is a non-prime attribute.. so I think it is also a partial dependency. 0 votes 0 votes Please log in or register to add a comment.
1 votes 1 votes In the above question there are 2 partial dependencies X->YZ and V->XY because Y is a non prime attribute which is depending on a part of candidate keys( UX,UV,UZ ) Mk Utkarsh answered Oct 25, 2017 • edited Oct 25, 2017 by Mk Utkarsh Mk Utkarsh comment Share Follow See all 0 reply Please log in or register to add a comment.
0 votes 0 votes Candidate keys are: XU,ZU,VU Prime attributes={X,U,Z,V} So,partial dependency is in:X->YZ,V->XY and there exists no dependency in Z->V because they both are prime attributes. Purvi Agrawal answered Mar 14, 2017 Purvi Agrawal comment Share Follow See all 0 reply Please log in or register to add a comment.
0 votes 0 votes Candidate Keys: UX , UV and UZ Prime Attributes: { U, V, X, Z} All the three FD are partial dependencies. (directly or indirectly after RHS split) As a proper subset of Candidate keys gives non-prime attributes. smsubham answered Aug 16, 2017 smsubham comment Share Follow See all 0 reply Please log in or register to add a comment.