Awesome q2a theme
0 votes
11 views

Relation R(ABCDE) with FD set $F=\left \{ A\rightarrow BC,C\rightarrow DE,D\rightarrow E \right \}$

and decomposition are $R1\left ( ABCD \right )$ and $R2\left ( DE \right )$


Now my question is $C\rightarrow DE$ dependency preserved? They told it is preserved, because 

$C\rightarrow D$ and $D\rightarrow E$ these two dependencies preserving and that is why $C\rightarrow DE$ also preserving. Is it true?

in Databases by (817 points) | 11 views
0
C -> D is preserved in the first relation, D -> E in the second one.

Now when we want to check if C -> DE is preserved, we consider the union of the FDs obtained from the decomposed relations and then try whether we are able to get what we need or not. So in this case, we have C -> D and D -> E with us.

When we take closure of C, we get C -> CDE, and thus, we are able to get C - > DE in this decomposition.
0
U mean transitive dependency?We have to check transitive dependency to check some dependency valid or not? Can u give me some resource?
There is no dependency directly from $C\rightarrow E$, is it not a violation of dependency?

Please log in or register to answer this question.

Quick search syntax
tags tag:apple
author user:martin
title title:apple
content content:apple
exclude -tag:apple
force match +apple
views views:100
score score:10
answers answers:2
is accepted isaccepted:true
is closed isclosed:true
Top Users 2020 Aug 10 - 16
  1. jayeshasawa001

    11 Points

  2. Arkaprava

    6 Points

  3. Nilabja Sarkar

    4 Points

  4. 404 found

    3 Points

  5. shashankrustagi2021

    2 Points

  6. Ashutosh777

    2 Points

  7. Mellophi

    2 Points

  8. siddharths067

    1 Points

  9. sparshgarg

    1 Points

  10. sonam13

    1 Points

Weekly Top User (excluding moderators) will get free access to GATE Overflow Test Series for GATE 2021
Welcome to GATE CSE Doubts, where you can ask questions and receive answers from other members of the community.
Top Users Aug 2020
  1. Mellophi

    152 Points

  2. Ashutosh777

    78 Points

  3. anurag sharma

    48 Points

  4. jayeshasawa001

    16 Points

  5. Kushagra गुप्ता

    15 Points

  6. Shaik Masthan

    13 Points

  7. srestha

    13 Points

  8. shashankrustagi2021

    12 Points

  9. munishchaturvedi

    10 Points

  10. arjun12

    10 Points

7,745 questions
1,842 answers
11,186 comments
95,103 users