Questions tagged [functional-dependencies]
The functional-dependencies tag has no usage guidance.
10
questions
2
votes
0
answers
42
views
Is there a functional programming language with inherent change propagation?
Change propagation in programming environments is an add-on at the framework level such as React.
There was a lot of work on dataflow virtual machines in the wake of Backus's Turing Award Lecture on ...
- 386
0
votes
1
answer
416
views
Relation is in 2NF or not?
Consider a relation R(A,B,C,D,E) and the only FDs,
ABD->C
BC->D
CD->E
These are the only 3 FDs. I want to know if the above relation is in 2NF or not.
According to the definition of 2NF, a ...
- 11
0
votes
1
answer
458
views
Find number of candidate keys given non-trivial functional dependency X->Y, where X is some set of attributes and Y is some prime attribute
In a relation R, if X is some set of attributes and Y is some prime attribute such that X uniquely determines Y is a non-trivial FD. Then is it true that R has at least two candidate keys?
For ...
- 147
1
vote
1
answer
249
views
Functional dependencies on relational schema
Given a relational schema $R(V,W,X,Y,Z)$ with functional dependencies $F = \{VW \to X, X \to YZ, W \to VX, V \to W, Z \to XY\}$. What are the keys of $R$?
Is the key just $V$? If so, is $\{ R_2(V,W,...
- 11
0
votes
1
answer
453
views
Database Theory - Does the dependency preservation and lossless join properties hold for every decomposition of a relation into 3NF?
I was reading Database Systems, 6th ed by Ramez Elmasri and Shamkant Navathe. In the textbook they make a claim (in Chapter 15, section 15.2 Properties of Relational Decompositions) which I quote ...
- 9
0
votes
1
answer
30
views
Functional dependencies , minimizing SUU->V
Can SUU->V or any functional dependency that contains two or more times each attribute be simplified to the same dependency with one attribute? So SUU->V becomes SU->V or STTT->Q becomes ST->Q ?
user102382
5
votes
1
answer
128
views
"Functional dependencies" with cardinality constraints
Let us write $\{ A_1, \ldots, A_k\} \rightrightarrows^n \{B_1, \ldots, B_m\}$ for a relation $R$ if for all $\langle a_1, \ldots, a_k\rangle$ we have $\left\lvert \pi_{B_1, \ldots, B_m} \sigma_{\...
- 171
0
votes
1
answer
134
views
Normal form after decomposition of a relation
I came across a text recently which claims that if we perform a lossless decomposition of a relation R into smaller relations R1 and R2, and if R is in 3NF, both R1 and R2 are 3NF.
I felt a bit ...
- 321
0
votes
3
answers
2k
views
Functional Dependencies
Let relational schema R(A,B,C,D,E,F,G,H,I).
The functional dependencies are: A -> BC, AD -> BE, C ->F , A->F , D-> E
Find the number of non-trivial functional dependencies ? I know that R has only ...
0
votes
1
answer
63
views
Given a relation and asked to enumerate all FD's and mark the trivial FD's
Given a relation R(A,B,C) and a FD set (A->B, B->C), find the FD Closure. Enumerate all the FD's and organize them accordingly to the LHS of the FD's. Mark all the trivial FD's.
I am a little ...
- 113