search
Log In

Recent questions tagged decomposition

0 votes
0 answers
1
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 Raj Kumar 7 222 views
1 vote
1 answer
2
Is minimal set of functional dependency for a functional dependency set is always unique???
asked Dec 10, 2018 in Databases gatecrack 134 views
1 vote
1 answer
3
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 ?
asked Jun 23, 2018 in Databases karthikmenon 239 views
0 votes
1 answer
4
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 $M\rightarrow O, NO\rightarrow P, P\rightarrow L, L\rightarrow MN$
asked May 1, 2018 in Databases Durgesh Singh 173 views
1 vote
1 answer
5
0 votes
0 answers
6
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?
asked Dec 12, 2017 in Databases rahul sharma 5 104 views
1 vote
2 answers
7
$R(X,Y,Z,W) is\ decomposed\ into \\ R_1(X,Y)\\ R_2(Y,Z)\\ R_3(Y,W).\\The\ FDs\ are\ :\\ X -> Y,\\ Z->Y,\\ Y->W \\ Find\ whether\ the\ decomposition\ is\ lossless\ or\ lossy\ ?$
asked Dec 8, 2017 in Databases Tuhin Dutta 228 views
2 votes
1 answer
8
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.
asked Dec 6, 2017 in Databases junaid ahmad 191 views
0 votes
2 answers
9
1 vote
2 answers
10
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 __________________________.
asked Nov 14, 2017 in Databases Manoja Rajalakshmi A 353 views
2 votes
2 answers
11
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.
asked Sep 30, 2017 in Databases Aman Bisht 1 295 views
0 votes
2 answers
12
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
asked Sep 21, 2017 in Databases rishu_darkshadow 188 views
0 votes
1 answer
13
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(B, C) = {B ... 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.
asked May 3, 2017 in Databases Shubhanshu 247 views
8 votes
2 answers
14
$X$ 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 ?
asked Feb 1, 2017 in Databases dd 949 views
2 votes
2 answers
15
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
asked Jan 12, 2017 in Databases sanyam53 310 views
1 vote
1 answer
17
0 votes
1 answer
18
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)
asked Nov 3, 2016 in Databases Chetnawadhwa 217 views
1 vote
1 answer
19
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 lossless. II. The decomposition of $R$ into $R1(A, B)$ and $R2(B, C)$ is lossy. Only $I$ Only $II$ Both $I$ and $II$ Neither $I$ nor $II$
asked Sep 30, 2016 in Databases makhdoom ghaya 596 views
4 votes
1 answer
20
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 relations, can we apply ... join property ? Or is that table drawing thing the only way to check for lossless join property ? Answers with reference(s) will be much appreciated. Thanks.
asked Sep 22, 2016 in Databases Rounak Agarwal 643 views
2 votes
3 answers
21
Decomposition help in eliminating some of the problems of bad design Redundancy Inconsistencies Anomalies All of the above
asked Aug 24, 2016 in Others makhdoom ghaya 656 views
3 votes
1 answer
22
The relation schemas $R_1$ and $R_2$ form a Lossless join decomposition of $R$ if and only if $R_1 \cap R_2 \twoheadrightarrow (R_1-R_2)$ $R_1 \rightarrow R_2$ $R_1 \cap R_2 \twoheadrightarrow (R_2-R_1)$ $R_2 \rightarrow R_1 \cap R_2$ a and b happen a and d happen a and c happen b and c happen
asked Jul 31, 2016 in Databases jothee 1.2k views
1 vote
2 answers
23
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 ($\rightarrow$ ... $R_1 \cap R_2 \rightarrow R_2$ $(R_1 \cap R_2) \rightarrow R_1 \text{ and } R_1 \cap R_2 \rightarrow R_2$
asked Jul 13, 2016 in Databases jothee 888 views
1 vote
4 answers
24
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
asked Jan 24, 2016 in Databases Purple 2.3k views
0 votes
3 answers
25
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,R2,R3,R4}: R1={M,N,O,P}, R2={M,P,Q}, R3= {N,R}, ... R4= {R,S,T} Which of the above decomposition (s) has/ have lossless join property? A. Only D1 B. Only D2 C. Both D1 and D2 D. Neither D1 nor D2
asked Jan 24, 2016 in Databases Purple 1.1k views
2 votes
2 answers
26
For which of the following set of functions dependencies does the relation $R(A, B, C, D)$ has $AB, CD$ as closed sets? $A \rightarrow B, B \rightarrow A, C \rightarrow D$ $A \rightarrow B, B \rightarrow C, C \rightarrow D, D \rightarrow A$ $A \rightarrow B, B \rightarrow A, C \rightarrow A, D \rightarrow A$ $A \rightarrow B, B \rightarrow A, C \rightarrow D, D \rightarrow C$
asked Dec 25, 2015 in Databases shiva 609 views
0 votes
2 answers
27
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
asked Aug 22, 2015 in Databases Tendua 132 views
1 vote
3 answers
29
Given a relation R(A, B, C) with functional dependencies set {A → B, B → C, C → B} (i) lossless decomposition is always possible for R (ii) Dependency preserving decomposition is always possible for R. Assume decomposition includes all the attributes ... ) Both (i) and (ii) are false Please explain your answer and what does Assume decomposition includes all the attributes of R mean?
asked Jan 7, 2015 in Databases Keith Kr 1.8k views
To see more, click for the full list of questions or popular tags.
...