63 votes 63 votes Relation $R$ with an associated set of functional dependencies, $F$, is decomposed into $\text{BCNF}$. The redundancy (arising out of functional dependencies) in the resulting set of relations isZeroMore than zero but less than that of an equivalent $3\text{NF}$ decompositionProportional to the size of $F^+$ Indeterminate Databases gatecse-2002 databases database-normalization normal + – Kathleen asked Sep 15, 2014 • edited Feb 16, 2018 by dj_1 Kathleen 20.5k views answer comment Share Follow See all 9 Comments See all 9 9 Comments reply Show 6 previous comments Aanshi Dua commented Dec 21, 2016 reply Follow Share Any good references to study MVDs? 0 votes 0 votes set2018 commented Oct 9, 2017 reply Follow Share based on functional dependency BCNF has 0 percent redundancy ,but is there any chance for other type redundancy m not getting other type ?explain pls 0 votes 0 votes Venky8 commented May 4, 2021 i edited by Venky8 May 4, 2021 reply Follow Share @set2018 A table is in 4NF if it is in BCNF and it should not have any multivalued dependencies. Databases with multivalued dependencies exhibit redundancy. So redundancy arising out of functional dependencies is 0 in BCNF but if the table has any multivalued dependencies then it has redundancy due to the multivalued dependencies. See Ref: 1. https://en.wikipedia.org/wiki/Multivalued_dependency#Example 2. https://www.studytonight.com/dbms/fourth-normal-form.php 1 votes 1 votes Please log in or register to add a comment.
Best answer 71 votes 71 votes Answer is A. If a relation schema is in BCNF then all redundancy based on functional dependency has been removed, although other types of redundancy may still exist. A relational schema R is in Boyce–Codd normal form if and only if for every one of its dependencies X → Y, at least one of the following conditions hold: X → Y is a trivial functional dependency (Y ⊆ X) X is a super key for schema R http://en.wikipedia.org/wiki/Boyce%E2%80%93Codd_normal_form Priya_das answered Jan 27, 2015 • edited Jun 22, 2018 by Milicevic3306 Priya_das comment Share Follow See all 13 Comments See all 13 13 Comments reply Digvijay Pandey commented May 15, 2015 reply Follow Share question is redundancy (arising out of functional dependencies) in the resulting set of relations is ? there is no redundancy due to FDs. Should be A ?? 0 votes 0 votes Priya_das commented May 18, 2015 reply Follow Share Yes .ans is A 0 votes 0 votes Shivansh Gupta commented Nov 27, 2016 reply Follow Share please give an example where redundancy due to functional dependencies exist. ? I am not getting what is diff between redundancy due to functional dependency and due to other reasons.. 10 votes 10 votes Agnel A commented Jan 14, 2018 reply Follow Share if BCNF has multivalued dependencies..then redundancy will happen? right..? 4 votes 4 votes srestha commented Jul 11, 2018 reply Follow Share Relation that have redundant data problem called anomalies. Anomalies can only removed by normalization. 1st NF talks about atomic values and non-repeating groups. 2nd NF enforces that a non-Key attribute should belong to entire Key attribute. 3rd NF makes sure that there should be no transitive dependency between a non-Key and a Key attribute. and Redundancy allowed by 3NF is disallowed by BCNF BCNF is stricter than 3NF 3NF is stricter than 2NF http://nptel.ac.in/courses/IIT-MADRAS/Intro_to_Database_Systems_Design/pdf/6_Relational_Schema_Design.pdf https://www.slideshare.net/jenspatel/data-redundancy-update-anomalies 7 votes 7 votes rajinder singh commented Nov 25, 2018 reply Follow Share Redundancy more than 0 Because Example table R(A,B) Tuples are (A1,b1),(A2,b1),(A3,b1),(A4,b1)(A5,b1).............(An,b1) Here Attribute A is primary key so relation in bcnf but if you see attribute B there redundancy so we can't say bcnf has 0 redundancy.so option b correct. 0 votes 0 votes Ajit J commented Nov 28, 2018 reply Follow Share So why is the answer to this question is false? If the number of redundancies are zero, then the answer to this should have been true? 0 votes 0 votes mrinmoyh commented Jul 22, 2019 reply Follow Share @srestha mam If we consider the rajinder singh case in the previous comment, then we can form a FD like A->B, but then also the relation is in BCNF & it has duplicate tuples. here A is a key & A->B satisfies the BCNF condition, but attribute B has redundant values. 0 votes 0 votes neeraj_bhatt commented Nov 20, 2019 reply Follow Share @Srestha mam Can you please update the NPTEL link? 0 votes 0 votes Jean commented Mar 22, 2020 reply Follow Share Multi valued dependency is also a type of FD right? 0 votes 0 votes prithatiti commented Apr 5, 2020 i edited by prithatiti Apr 5, 2020 reply Follow Share (C) Proportional to the size of F+ I really didn't understand this option. What does it mean by the size of the F closure? 0 votes 0 votes aditya_cracks2021 commented Nov 18, 2020 reply Follow Share Yes, it's the size of closure. 0 votes 0 votes KartikGawande commented Nov 25, 2022 reply Follow Share Jean no Multivalued Dependencies doesnt follow armstrong axioms like decomposition etc so they r NOT a type of FD 0 votes 0 votes Please log in or register to add a comment.
42 votes 42 votes should be zero.. BCNF can have Multi valued dependency but no redundancy due to FDs.. Digvijay Pandey answered May 15, 2015 • edited May 15, 2015 by Digvijay Pandey Digvijay Pandey comment Share Follow See all 9 Comments See all 9 9 Comments reply Show 6 previous comments srestha commented Sep 5, 2019 reply Follow Share 1NF is atomic relation. I donot think attribute depends on it. Multivalued dependency is not in 1NF. 0 votes 0 votes ayushsomani commented Sep 6, 2019 reply Follow Share @srestha Thanks. I got it now. In 1NF we make attributes atomic, either by removing Composite attributes (by breaking them into simpler attributes), or, Multi-valued attributes (by making a new tuple for each 'value' in Multi-valued attribute) Multi-valued Dependency is removed in 4NF. 0 votes 0 votes prithatiti commented Apr 5, 2020 i edited by prithatiti Apr 5, 2020 reply Follow Share @srestha In 4NF we remove the multivalued dependency. That means in BCNF multi-valued dependencies might be present. Because in 4NF, the table must be present in the form of BCNF. Correct me if I am wrong. 0 votes 0 votes Please log in or register to add a comment.
6 votes 6 votes Yes , the answer should be zero. There should not be any redundancy due to FD in BCNF. worst_engineer answered May 15, 2015 • edited May 15, 2015 by worst_engineer worst_engineer comment Share Follow See all 2 Comments See all 2 2 Comments reply Digvijay Pandey commented May 15, 2015 reply Follow Share **redundancy. There should not be any //dependency due to FD in BCNF. 0 votes 0 votes worst_engineer commented May 15, 2015 reply Follow Share ohh yaa.. typos there.. correcting it..thanks :) 0 votes 0 votes Please log in or register to add a comment.
1 votes 1 votes Explain please BCNF can have Multi valued dependency but no redundancy due to FDs flash12 answered Dec 16, 2018 flash12 comment Share Follow See all 0 reply Please log in or register to add a comment.