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Recent questions tagged functional-dependencies
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1
Made Easy Test Series:DBMS-Functional Dependency
Consider a relation $R\left ( A,B,C,D,E \right )$ and functional dependencies are $F=\left \{ AC\rightarrow B,C\rightarrow D,A\rightarrow E,C\rightarrow B \right \}$ Relation $R$ ... Then Is it a lossless decomposition? I am getting doubt, how it can be not lossless decomposition?
asked
Apr 28
in
Databases
by
srestha
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117k
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112
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functional-dependencies
databases
lossless-decomposition
0
votes
2
answers
2
Molina Exercise-3.3 BCNF decomposition
Decompose into BCNF R(A, B, C, D, E) FD: AB->C, C->D, D>B, D->E
asked
Apr 14
in
Databases
by
aditi19
Active
(
5.1k
points)
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184
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functional-dependencies
database-normalization
databases
bcnf-decomposition
bcnf
0
votes
1
answer
3
made easy test series - lossless join and dependency preserving
How is A answer?
asked
Apr 7
in
Databases
by
amitqy
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1.8k
points)
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91
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lossless-decomposition
databases
dependency-preserving
functional-dependencies
0
votes
0
answers
4
Doubt
Do we need to find closure of functional dependencies of original relation to check whether the decomposed tables are in 2NF . I know that we have to do the above process for 3NF and BCNF . If yes , please give a example where we need to do it
asked
Mar 30
in
Databases
by
ashunimbz
(
59
points)
|
17
views
functional-dependencies
relational-model
+2
votes
1
answer
5
GATE2019-32
Let the set of functional dependencies $F=\{QR \rightarrow S, \: R \rightarrow P, \: S \rightarrow Q \}$ hold on a relation schema $X=(PQRS)$. $X$ is not in BCNF. Suppose $X$ is decomposed into two schemas $Y$ and $Z$, where $Y=(PR)$ ... $Y$ and $Z$ is dependency preserving and lossless Which of the above statements is/are correct? Both I and II I only II only Neither I nor II
asked
Feb 7
in
Databases
by
Arjun
Veteran
(
425k
points)
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2.1k
views
gate2019
databases
functional-dependencies
0
votes
0
answers
6
Ace Test Series: DBMS - Functional Dependency
asked
Jan 21
in
Databases
by
Na462
Loyal
(
6.9k
points)
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56
views
functional-dependencies
databases
ace-test-series
0
votes
0
answers
7
self doubt - NO. of tables after normalizing
Are 3NF decompostions and BCNF decompostions unique? Are 4NF important for GATE (since I've left them :( ) See, I am asking this question because I want to know whether they'll ask about no. of tables we get after normalizing upto 3nf or bcnf. Now ... I am in a bit hurry to search for that.. so please forgive me if it has been already asked.) Thank you.
asked
Jan 21
in
Databases
by
Harsh Kumar
Active
(
1.3k
points)
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38
views
databases
relational
functional-dependencies
bcnf-decomposition
3nf-decomposition
database-normalization
0
votes
0
answers
8
Self-doubt | DBMS | Functional Dependency
Can someone explain the paragraph marked based on relation $r$ given in Figure 7.2? Reference: Database System Concepts by Silberschatz, Korth, Sudarshan 4th Edition.
asked
Jan 5
in
Databases
by
zeeshanmohnavi
Junior
(
915
points)
|
38
views
functional-dependencies
databases
0
votes
1
answer
9
MadeEasy Test Series: Databases - Functional Dependencies
Consider the following relation R(A, B, C, D, E, F, G) and set of functional dependencies. F={BCD → A, BC → E, A → F, F → G, A→G, C → D} Which of the following is minimal cover of F? (A) {BC → A, BC → E, A → F, C → D, A → G} (B) ... → D} (D) {BC → A, BC → E, A → F, C → D} My doubt here is Since (B) covers F, why can't it be a minimal cover?
asked
Jan 5
in
Databases
by
Shivam Kasat
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(
3.2k
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92
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made-easy-test-series
databases
minimal-cover
functional-dependencies
0
votes
0
answers
10
Sel doubt
Relation R (A,B,C,D,E,F) Functional dependency: ABC -->DEF, BC-->EF, EF-->D. Decomposition: R1 (ABCDF), R2 (BCDE). Is this decomposition lossy? Is this decomposition preserve functional dependency? Plz explain how to check functional dependency is preserved or not in decomposition.
asked
Dec 24, 2018
in
Databases
by
Raj Kumar 7
Active
(
1.1k
points)
|
136
views
databases
functional-dependencies
decomposition
+1
vote
1
answer
11
ME test series
Consider relation R(A,B,C,D,E,F,G) with the following functional dependencies AB$\rightarrow$CD , D$\rightarrow$B, AF$\rightarrow$D, DE$\rightarrow$F, C$\rightarrow$G, F$\rightarrow$E, G$\rightarrow$A. What is the highest normal form.
asked
Dec 20, 2018
in
Databases
by
Rajat Agrawal007
Junior
(
665
points)
|
77
views
functional-dependencies
+1
vote
2
answers
12
MadeEasy Test Series: Databases - Functional Dependencies
Consider Relation R(A,B,C,D,E,F,G) and set of Functional dependencies: F = {BCD → A, BC→ E, A→ F, F→ G, C→ D, A→ G} What is the minimal cover of F ? Answer given: BC → A, BC→ E, A→ F, F→ G, C→ D Why the answer cant be: BC → A, BC→ E, A→ F, C→ D, A→ G
asked
Dec 20, 2018
in
Databases
by
Shamim Ahmed
Active
(
2.4k
points)
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149
views
made-easy-test-series
databases
functional-dependencies
0
votes
1
answer
13
MadeEasy Test Series: Databases - Functional Dependencies
asked
Dec 19, 2018
in
Databases
by
Vaishnavi01
(
143
points)
|
67
views
made-easy-test-series
databases
functional-dependencies
minimal-cover
+1
vote
1
answer
14
Self doubt dbms Normalisation
Is minimal set of functional dependency for a functional dependency set is always unique???
asked
Dec 10, 2018
in
Databases
by
gatecrack
(
279
points)
|
95
views
databases
decomposition
lossless-join
database-normalization
functional-dependencies
+3
votes
1
answer
15
MadeEasy Test Series: Databases - Functional Dependencies
Consider the relation R(A,B,C,D,E) with the functional dependencies : A → B, B → C, C → A, D → E, and E → D The Maximum possible super-keys of R is ______________?
asked
Dec 7, 2018
in
Databases
by
naveen bhatt
Junior
(
751
points)
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186
views
made-easy-test-series
databases
functional-dependencies
superkeys
0
votes
1
answer
16
Functional preserving
Given $R(A,B,C,D,E)$ and $F:\left \{A\rightarrow BC ,CD\rightarrow E,B\rightarrow D,E\rightarrow A\right \}$,Decompose into $BCNF?$ $(a)$Every $BCNF$ is $3NF$ and vice versa $?$ $(b)FD$ preserving or not$?$ $(c)$ Lossless decomposition or lossy decomposition?
asked
Nov 20, 2018
in
Databases
by
Lakshman Patel RJIT
Veteran
(
54.8k
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275
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databases
database-normalization
functional-dependencies
dependency-preserving
lossless-decomposition
0
votes
0
answers
17
#Self Doubt
In definition of transitive dependency we use conditions as A → B It is not the case that B → A B → C I am not able to understand why we need condition 2 for this ?
asked
Nov 6, 2018
in
Databases
by
Rameesh
(
435
points)
|
139
views
databases
database-normalization
functional-dependencies
0
votes
0
answers
18
MadeEasy Workbook: Databases - Functional Dependencies
F={AB->C,A->B} FIND EXTRANEOUS ATTRIBUTE ??
asked
Oct 31, 2018
in
Databases
by
amit166
Junior
(
761
points)
|
51
views
databases
functional-dependencies
made-easy-workbook
0
votes
2
answers
19
#madenotes
A B C 1 1 1 1 1 0 2 3 2 2 3 2 FIND NON-TRIVIAL DEPENDENCY
asked
Oct 31, 2018
in
Databases
by
amit166
Junior
(
761
points)
|
69
views
functional-dependencies
+2
votes
1
answer
20
Ace Test Series: DBMS - Canonical Cover In FD
asked
Oct 29, 2018
in
Databases
by
tusharforever
(
155
points)
|
112
views
databases
ace-test-series
functional-dependencies
minimal-cover
+1
vote
1
answer
21
#Functional Depencency
max number of FD in a relation with 'n' attributes=$2^{2n}$ how this formula is obtained?
asked
Oct 28, 2018
in
Databases
by
aditi19
Active
(
5.1k
points)
|
75
views
functional-dependencies
databases
database-normalization
0
votes
2
answers
22
Self Doubt
A relation R is in 2NF if every non-prime attribute of R is fully functionally dependent on every key of R true or false R(A,B,C) F {A->B,B->C} Here key = A R is in 2NF So is C is fully functional dependent on every key here ?. It is not dependent on key infact ?
asked
Oct 24, 2018
in
Databases
by
jatin khachane 1
Loyal
(
7.3k
points)
|
68
views
databases
database-normalization
functional-dependencies
0
votes
0
answers
23
Self Doubt
While checking for normal forms Why we only check conditions only on F not on F+ eg R(A,B,C) F = {A->B , B->C} is in 3NF or not ? We will apply defination of 3NF i,e either LHS should be super key or RHS should be prime attribute ON ... if decomposed relation is in particular normal form we apply check on ALL IMPLIED FDs from F ?? In below ex should all implied FDs be checked ??
asked
Oct 23, 2018
in
Databases
by
jatin khachane 1
Loyal
(
7.3k
points)
|
38
views
databases
database-normalization
computer-networks
functional-dependencies
0
votes
0
answers
24
Self doubt
Can Prime attribute be NULL in any of the the Candidate key ?? Can Prime attribute be NULL in Primary key ??
asked
Oct 23, 2018
in
Databases
by
jatin khachane 1
Loyal
(
7.3k
points)
|
36
views
databases
candidate-keys
functional-dependencies
0
votes
0
answers
25
Second Normal Form
asked
Oct 21, 2018
in
Databases
by
Na462
Loyal
(
6.9k
points)
|
153
views
database-normalization
functional-dependencies
databases
0
votes
1
answer
26
Normalisation
Difference between composite and compound key??
asked
Oct 5, 2018
in
Databases
by
Raghav Khajuria
Junior
(
761
points)
|
66
views
database-normalization
functional-dependencies
0
votes
0
answers
27
Normalization
asked
Oct 4, 2018
in
Databases
by
Vaishnavi01
(
143
points)
|
74
views
databases
functional-dependencies
database-normalization
+1
vote
2
answers
28
Lossless Decomposition and Dependency Preservation
Consider R(A,B,C,D,E)with the FD Set F(A->B, A->C, DE->C, DE->B, C->D) Consider this decomposition : R1(A,B,C), R2(B,C,D,E) and R3(A,E) Then, the decompositions is Lossless Decomposition Dependency Preserving Which of the ... 1 is TRUE but 2 is FALSE B) 1 is FALSE but 2 is TRUE C) Both 1 and 2 are TRUE D) Both 1 and 2 are FALSE
asked
Sep 27, 2018
in
Databases
by
Balaji Jegan
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(
4.9k
points)
|
213
views
dependency-preserving
databases
lossless-decomposition
functional-dependencies
0
votes
0
answers
29
Normalization - transitive dependency
In the books, it is written that a transitive dependency is one in which a non-key attribute is determining another non-key attribute. So, if ${R (A,B,C,D,E,F)}$ be a relation and ${ABC}$ ... about those dependencies in which the LHS is a combination of key and non-key attributes ? for example, what about ${ABD \to E}$ ?
asked
Sep 15, 2018
in
Databases
by
Harsh Kumar
Active
(
1.3k
points)
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82
views
database-normalization
functional-dependencies
0
votes
0
answers
30
Testbook Test Series: Databases - Functional Dependencies
Consider a relation R(A,B,C,D,E,F,G) with set of functional dependencies F={AD->BF, CD->EGC, BD->F, E->D, F->C, D->F} The relation R is ... dependency preserving Decomposition is lossy and dependency preserving Decomposition is lossy and not dependency preserving Decomposition is lossless and not dependency preserving
asked
Aug 21, 2018
in
Databases
by
Mk Utkarsh
Boss
(
35.7k
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105
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testbook-test-series
databases
functional-dependencies
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