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Recent questions tagged decomposition

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1

2NF DECOMPOSITION

ROMITDUTTA asked in Databases Jul 5, 2023

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1 vote

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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.

Raj Kumar 7 asked in Databases Dec 24, 2018

1.1k views

2 votes

2 answers

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Self doubt dbms Normalisation
Is minimal set of functional dependency for a functional dependency set is always unique???

gatecrack asked in Databases Dec 10, 2018

603 views

2 votes

2 answers

4

Function Dependency question
Consider a relation R(A,B,C,D,E,F,H) with A as the only key. Assume that the dependencies E->F and C-> DEH hold.on R. 1. Is R in 2NF? If not, decompose to 2NF. 2. is R in 3NF? if not, decompose to 3NF. //What does " with A as the only key" mean ?

karthikmenon asked in Databases Jun 23, 2018

by karthikmenon

1.0k views

1 vote

1 answer

5

Self - Doubt : How to calculate candidate keys in decomposed Relation?
For relation R=(L, M, N, O, P), the following dependencies hold and R is decomposed into R1 = (L, M, N, P) and R2 = (M, O). How to calculate what candidate keys are there for relation R1 and R2. Please tell me the algorithm. FD's are $M\rightarrow O, NO\rightarrow P, P\rightarrow L, L\rightarrow MN$

Durgesh Singh asked in Databases May 1, 2018

by Durgesh Singh

785 views

1 vote

1 answer

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Mk Utkarsh asked in Databases Jan 12, 2018

1.0k views

0 votes

0 answers

7

DBMS Losless join
R is divided into R1 and R2 ,but since there is no common attribute in R1 and R2, so it should form lossy join,as for loseless join the common attribute has to be key in one of the table.But here the image above,it is comming as loseless join.Can someone please check?

rahul sharma 5 asked in Databases Dec 12, 2017

by rahul sharma 5

476 views

1 vote

2 answers

8

lossless join
$R(X,Y,Z,W) is\ decomposed\ into \\ R_1(X,Y)\\ R_2(Y,Z)\\ R_3(Y,W).\\The\ FDs\ are\ :\\ X -> Y,\\ Z->Y,\\ Y->W \\ Find\ whether\ the\ decomposition\ is\ lossless\ or\ lossy\ ?$

Tuhin Dutta asked in Databases Dec 8, 2017

612 views

2 votes

1 answer

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NORMALIZTION
Q.Let R (X, Y, Z, W) be a relational schema with the following functional dependencies: X→ Y, Y → Z, Z → W and W → Y. The decomposition of R into (X, Y), (Y, Z), (Y, W) it is asked to find whether it is lossless join and dependency preserving or not ? I am sure it is lossless join,but couldn't figure how it is dependency preserving.

junaid ahmad asked in Databases Dec 6, 2017

by junaid ahmad

2.0k views

3 votes

2 answers

10

2NF decomposition
How is it option D??

Parshu gate asked in Databases Nov 19, 2017

3.6k views

1 vote

2 answers

11

virtual gate
Relation R(ABCDEF) with the following set of functional dependencies {AB→CDEF, C→A, D→B, E→F, B→E}. The decomposed relationslations of R into 3NF are __________________________.

Manoja Rajalakshmi A asked in Databases Nov 13, 2017

by Manoja Rajalakshmi A

3.2k views

2 votes

2 answers

12

lossless decomposition
I know the condition for a 2 table to be lossless, but i cannot visualize it. How is 1 table which is decomposed, and if common attribute is key in any one of table, then its lossless decomposition. Can anyone explain me this with different analogy or help me visualize it.

Aman Bisht 1 asked in Databases Sep 29, 2017

by Aman Bisht 1

705 views

0 votes

2 answers

13

DBMS-Decomposition
Which of the following statement is true while decomposition ? 3NF guaranteed dependency preserving 3NF guaranteed lossless property Both of the above None of the above

rishu_darkshadow asked in Databases Sep 21, 2017

by rishu_darkshadow

592 views

0 votes

1 answer

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Testing Lossless join
State true or false:- Symbol " ^ " stands for an intersection AND letters in bold are the candidate key of the respective table. 1) R1(A, B, C) ^ R2(B, C) = {B,C} IS LOSSLESS JOIN. 2) R1(A, B, C) ^ R2(B, D) = {B} IS LOSSY JOIN. 3) R1(A, B ... C), R2(D, E), R3(F, B), R4(D, G, A) Also, tell what will be the candidate key after performing join each time and at the end.

Shubhanshu asked in Databases May 3, 2017

637 views

8 votes

2 answers

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Higher normal form decomposition
$X$ is an entity set. $E$ and $F$ are multivalued attributes. How many minimum tables which satisfy 1NF ? How many minimum tables which satisfy 2NF ? How many minimum tables which satisfy 3NF ? How many minimum tables which satisfy BCNF ? How many minimum tables which satisfy 4NF ?

dd asked in Databases Feb 1, 2017

by dd

2.5k views

3 votes

2 answers

16

DBMS Normalisation
Consider a schema R(A, B, C, D) and functional dependencies {AB → C, C → D, D→ A}. Then the decomposition of R into R1 (CD), R2 (AC) and R3 (BC) is in a. 1NF but not 2NF b. 2NF but not 3NF c. 3NF but not BCNF d. BCNF

sanyam53 asked in Databases Jan 11, 2017

893 views

3 votes

4 answers

17

DBMS-Normalisation-Lossless Join Decomposition

KISHALAY DAS asked in Databases Dec 21, 2016

by KISHALAY DAS

1.2k views

2 votes

1 answer

18

Lossy join decomposition

Rakesh K asked in Databases Dec 9, 2016

1.3k views

0 votes

1 answer

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Database mgmt system
Tell whether the following decomposition of relations lossless and dependency preserving or not. 1. R(ABCDEFGHIJ) and FD sets AB->C, A->DE, B->F, F->GH, D->IJ a) D1"={ DIJ, ACE, FGH, BF, ADC} b) D2={ FGH, DIJ, ADEBF, ABC} 2.R(ABCDEG) and FD sets AB->C, AC->B, AD->E, B->D, BC->A, E->G a) D=( ABC, ACDE, ADG)

Chetnawadhwa asked in Databases Nov 2, 2016

by Chetnawadhwa

1.5k views

2 votes

1 answer

20

UGC NET CSE | August 2016 | Part 3 | Question: 10
Consider the table $R$ with attributes $A, B$ and $C$. The functional dependencies that hold on $R$ are : $A \rightarrow B, C \rightarrow AB$. Which of the following statements is/are True ? I. The decomposition of $R$ into $R1(C, A)$ and $R2(A, B)$ is ... $R1(A, B)$ and $R2(B, C)$ is lossy. Only $I$ Only $II$ Both $I$ and $II$ Neither $I$ nor $II$

makhdoom ghaya asked in Databases Sep 30, 2016

by makhdoom ghaya

2.0k views

4 votes

1 answer

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Checking for lossless-join property
The decomposition of relation R with FD set F into R1 and R2 has lossless join property iff R1 $\cap$ R2 $\rightarrow$ R1 $\in$ F$^+$ OR R1 $\cap$ R2 $\rightarrow$ R2 $\in$ F$^+$ If R is decomposed into more than 2 ... ? Or is that table drawing thing the only way to check for lossless join property ? Answers with reference(s) will be much appreciated. Thanks.

Rounak Agarwal asked in Databases Sep 22, 2016

by Rounak Agarwal

1.0k views

2 votes

3 answers

22

UGC NET CSE | June 2011 | Part 2 | Question: 20
Decomposition help in eliminating some of the problems of bad design Redundancy Inconsistencies Anomalies All of the above

makhdoom ghaya asked in Others Aug 23, 2016

by makhdoom ghaya

2.4k views

5 votes

1 answer

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UGC NET CSE | Junet 2015 | Part 3 | Question: 11
The relation schemas $R_1$ and $R_2$ form a Lossless join decomposition of $R$ if and only if $R_1 \cap R_2 \twoheadrightarrow (R_1-R_2)$ $R_1 \rightarrow R_2$ $R_1 \cap R_2 \twoheadrightarrow (R_2-R_1)$ $R_2 \rightarrow R_1 \cap R_2$ $\text{i and ii}$ happen $\text{i and iv}$ happen $\text{i and iii}$ happen $\text{ii and iii}$ happen

go_editor asked in Databases Jul 31, 2016

4.1k views

1 vote

2 answers

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UGC NET CSE | December 2012 | Part 3 | Question: 56
If a relation with a Schema R is decomposed into two relations $R_1$ and $R_2$ such that $(R_1 \cup R_2) = R_1$ then which one of the following is to be satisfied for a lossless joint decomposition ($\rightarrow$ indicates functional ... $(R_1 \cap R_2) \rightarrow R_1 \text{ and } R_1 \cap R_2 \rightarrow R_2$

go_editor asked in Databases Jul 13, 2016

3.0k views

2 votes

4 answers

25

Canonical cover of a set
Consider the following set of functional dependency on the scheme (A, B,C) A-->BC, B-->C, A--> B, AB-->C The canonical cover for this set is: (A) A-->BC and B--> C B. A-->BC and AB--> C C. A--> BC and A--> B D. A--> B and B--> C

Purple asked in Databases Jan 24, 2016

by Purple

18.0k views

1 vote

3 answers

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Which of the above decomposition has/ have lossless join property?
Consider a relation R= {M, N, O,P, Q, R, S, T} with the following set of dependencies: MN--> Q M--> RQ N--> R R--> ST Next consider the following set of decompositions for the relation schema R: D1= {R1, ... decomposition (s) has/ have lossless join property? A. Only D1 B. Only D2 C. Both D1 and D2 D. Neither D1 nor D2

Purple asked in Databases Jan 24, 2016

by Purple

6.4k views

2 votes

2 answers

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For which of the following set of functional dependencies does the relation R(A,B,C,D) has AB,CD as closed sets

shiva asked in Databases Dec 25, 2015

by shiva

2.6k views

0 votes

2 answers

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how to approach this type of question
i know how to find whether the decomposition is lossless or lossy . but in this type of question they are actually not defining how they decompose . they are only giving a set of functional depenencies . how to solve this type of question

Tendua asked in Databases Aug 22, 2015

by Tendua

394 views

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Recent questions tagged decomposition