# Recent questions tagged data-dependences

1
Consider a relational schema $S=(U,V,W,X,Y,Z)$ on which the following functional dependencies hold: $(U \rightarrow V, VW \rightarrow X, Y \rightarrow W, X \rightarrow U)$ Which are the candidate keys among following options? $UY, VY$ $UY, VY, XY$ $UYZ, VYZ, VWZ$ $UYZ, VYZ, XYZ$
2
A functional dependency of the form $x\to y$ is trivial if $y\subseteq x$ $y\subset x$ $x\subseteq y$ $x\subset y\:\text{and}\:y\subset x$
3
Given the following relation instance: $\begin{array}{ccc} X & Y & Z \\ \hline 1 & 4 & 2 \\ 1 & 5 & 3 \\ 1 & 6 & 3 \\ 3 & 2 & 2 \end{array}$ ... $YZ \rightarrow X \text{ and } X \rightarrow Z$ $XZ \rightarrow Y \text{ and } Y \rightarrow X$
4
Consider the schema $R=(\text{S T U V})$ and the dependencies $S \rightarrow T, T \rightarrow U, U \rightarrow V$, and $V \rightarrow S.$ If $R=(R1 \text{ and } R2)$ be a decomposition such that $R1 \cap R2= \phi$ then decomposition is not in $\text{2 NF}$ in $\text{2 NF}$ but not in $\text{3 NF}$ in $\text{3 NF}$ but not in $\text{2 NF}$ in both $\text{2 NF}$ and $\text{3 NF}$
5
Which of the following is a desirable property of module? Independency Low cohesiveness High Coupling Multifunctional
6
Which of the following is a desirable property of module? Independency Low cohesiveness High Coupling Multifunctional
7
Which statement is false regarding data independence ? Hierarchical data model suffers from data independence Network model suffers from data independence Relational model suffers only from logical data independence Relational model suffers only from physical data independence
8
The undesirable multivalued dependency in a relation arises if there exist Two one-to-many relationships between attributes of a relation One one-to-one and one one-to many one relationships between attributes within a relation Two one-to-one relationships between attributes of a relation One one-to-many relationship between attributes across relation
9
Please clarify along with the names.
10
Data forwarding is used to avoid which type of conflict?? (1) RAW (2) WAR (3) WAW (4) RAR
11
12
Consider the following functional dependencies in a database: $A \rightarrow B$ $B \rightarrow C$ $D \rightarrow E$ $E \rightarrow D$ $F \rightarrow G$ $F \rightarrow H$ $(E,F) \rightarrow 1$ The relation $(E,D,A,B)$ is $2$ NF $3$ NF BCNF None of the above
13
Find the data hazards(RAW,WAW,WAR) in the given instructions
14
$I_1 : MUL \ \ \ \ \ R_1, R_2, R_3$ // $R_1 \leftarrow R_2 \times R_3$ $I_2 : ADD \ \ \ \ \ R_4, R_4, R_1$ $I_3 : MUL \ \ \ \ \ R_1, R_5, R_6$ $I_4 : SUB \ \ \ \ \ R_4, R_4, R_1$ Sum of RAW, WAR and WAW dependencies is _____.
15
Consider the below instructions executed on a 5 stage(IF,ID,EX,MA,WB) RISC pipeline with operand forwarding. I1: ADD R0,R1,R2 (R0=R1+R2) I2: SUB R3,R0,R2 I3:MUL R4,R3,R0 I4:DIV R5,R4,R0 How many RAW dependencies?
16
Anti- dependency will not ALWAYS create stall because we can use register renaming to remove stall. Please confirm below statement: Anti-dependency MAY create stall (True/False)
17
I'm getting 6,1,2 but the answer given is 5,1,2
1 vote
18
J1: R1 = 100 J2: R1 = R2 + R4 J3: R2 = R4 + 25 J4: R4 = R1 + R3 J5: R1 = R1 + 30 Give the no of RAW, WAR and WAW hazards
19
R4 <- R1 + R4 R4 <- R2 + R4 R4 <- R3 + R5 Number of WAR and WAW dependencies?
20
R(ABCDE) { A,BC,CD} are candidate key of relation R after 1 NF design which one is possible multi valued attributes before 1 NF design ???
21
Number of WAR dependencies possible R1 <- R3 + R2 R3 <- R3 + R5 R3 <- R2 + R3 Is it 2 or 3?
22
1- R(ABCD) FD'S ARE {AB->C ,C->D,D->EA ,DE->F,EF->B} 2-R(ABCD) FDS ARE { A->BC, CD->E, B->D,E-A} 3- R(ABCD) {AB-> CD,C->B,D->C} Find the candidate key ??? For above questions and please explain too.
1 vote
23
Consider the following instructions. I​ 1​ : R​ 1​ = 100 I​ 2​ : R​ 1​ = R​ 2​ + R​ 4 I​ 3​ : R​ 2​ = R​ 4​ + 25 I​ 4​ : R​ 4​ = R​ 1​ + R​ 3 I​ 5​ : R​ 1​ = R​ 1​ + 30 Calculate sum of (WAR, RAW and WAW) dependencies the above instructions. (a) 10 (c) 6 (b) 12 (d) 8
1 vote
24
1 vote
25
For relation R=(L, M, N, O, P), the following dependencies hold: M→O, NO→P, P→Land L→MN R is decomposed into R1 = (L, M, N, P) and R2 = (M, O).What is the highest normal form satisfied by the above decomposition? My doubt is For R1 it is in 2NF and R2 it is in BCNF .But ,dependency preserving also violates .So whts the highest normal form ?