1 votes 1 votes Consider the relation R(ABCDE) with the FD set F={A-->E,BC-->D,E-->CD} . find the 3NF decomposition . Databases database-normalization databases + – Manisha Jaishwal asked Jun 5, 2022 • retagged Jun 5, 2022 by Kabir5454 Manisha Jaishwal 474 views answer comment Share Follow See all 10 Comments See all 10 10 Comments reply Show 7 previous comments Arjun commented Jun 6, 2022 reply Follow Share @Manisha Jaishwal What do previous year questions on database normalization say? 0 votes 0 votes Kabir5454 commented Jun 6, 2022 reply Follow Share @Arjun The relation given is R(ABCDE) The FD set given F={A->E,BC->D,E->CD} The Candidate key is =AB The algorithm to decomposed a relation to 3NF:- Eliminate redundant FD’s resulting in a canonical cover $F_{c}$ of $F$. Create a relation $R_{i}$=$XY$ for each FD $X→ Y$ in $F_{c}$. If the key K of $R$ does does not occurs in any relation $R_{i}$,Create one more relation $R_{i}$=$K$. If we try to compute the minimal cover for our given FD set we found out that $F$=$F_{c}$. So from step 2 of the algorithm the decomposed relations are :- AE,BCD,ECD Now in step 3 , the key $K$ of R does not occur in any relations $R_{i}$ so we have to add the key AB as another relation. so we have minimum $4$ decomposed relation $AB,AE,BCD,ECD$. BCNF is more stricter than 3NF but may not be dependency preserving which implies we are not always go for dependency preserving . so our main focus should be lossless join to reduce the redundancy of data .But in practice i believe we prefer 3NF which is easy to achieve. The algorithm link := https://faculty.ksu.edu.sa/sites/default/files/E-%20Decomposition.pdf 1 votes 1 votes Manisha Jaishwal commented Jun 7, 2022 reply Follow Share Thanks 🙏 0 votes 0 votes Please log in or register to add a comment.