Awesome q2a theme
0 votes

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 (635 points) | 8 views
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.
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
Welcome to GATE CSE Doubts, where you can ask questions and receive answers from other members of the community.
Top Users Jan 2020
  1. shashin

    1163 Points

  2. Vimal Patel

    306 Points

  3. Deepakk Poonia (Dee)

    305 Points

  4. Debapaul

    237 Points

  5. Satbir

    192 Points

  6. SuvasishDutta

    137 Points

  7. Pratyush Priyam Kuan

    118 Points

  8. tp21

    108 Points

  9. pranay562

    95 Points

  10. DukeThunders

    94 Points

Monthly Top User and those within 60% of his/her points will get a share of monthly revenue of GO subject to a minimum payout of Rs. 500. Current monthly budget for Top Users is Rs. 75.
2,983 questions
1,509 answers
89,814 users