Relational Schema

Question 1
Consider the following statements S1 and S2 about the relational data model:

S1: A relation scheme can have at most one foreign key.
S2: A foreign key in a relation scheme R cannot be used to refer to tuples of R.

Which one of the following choices is correct?
A
Both S1 and S2 are true
B
S1 is true and S2 is false
C
S1 is false and S2 is true
D
Both S1 and S2 are false
GATE CSE 2021 SET-2   Database Management System
Question 2
Consider the relation R(P,Q,S,T,X,Y,Z,W) with the following functional dependencies.

PQ\rightarrow X;\quad P\rightarrow YX;\quad Q\rightarrow Y; \quad Y\rightarrow ZW

Consider the decomposition of the relation R into the constituent relations according to the following two decomposition schemes.

D1:\quad R=[(P,QS,T);\;(P,T,X);\;(Q,Y);\;(Y,Z,W)]
D2:\quad R=[(P,Q,S);\;(T,X);\;(Q,Y);\;(Y,Z,W)]

Which one of the following options is correct?
A
D1 is a lossless decomposition, but D2 is a lossy decomposition.
B
D1 is a lossy decomposition, but D2 is a lossless decomposition.
C
Both D1 and D2 are lossless decompositions.
D
Both D1 and D2 are lossy decompositions.
GATE CSE 2021 SET-1   Database Management System
Question 3
Immunity of the external schemas (or application programs) to changes in the conceptual scheme is referred to as:
A
Physical Data Independence
B
Logical Data Independence
C
Both (A) and (B)
D
None of the above
ISRO CSE 2018   Database Management System
Question 4
Considering the following table in a relational database :
\begin{array}{|c|c|c|c|} \hline \text { Last Name } & \text { Rank } & \text { Room } & \text { Shift } \\ \hline \text { Smith } & \text { Manager } & 234 & \text { Morning } \\ \hline \text { Jones } & \text { Custodian } & 33 & \text { Afternoon } \\ \hline \text { Smith } & \text { Custodian } & 33 & \text { Evening } \\ \hline \text { Doe } & \text { Clerical } & 222 & \text { Morning } \\ \hline \end{array}
According to the data shown in the table, which of the following could be a candidate key of the table?
A
{Last Name}
B
{Room}
C
{Shift}
D
{Room, Shift}
ISRO CSE 2018   Database Management System
Question 5
What does a data dictionary will identify?
A
Field name
B
Field format
C
Field types
D
All of the above
ISRO CSE 2017   Database Management System
Question 6
Goals for the design of the logical scheme include
A
avoiding data inconsistency
B
being able to construct query easily
C
being able to access data efficiently
D
All of the above
ISRO CSE 2016   Database Management System
Question 7
Which of the following is NOT a superkey in a relational schema with attributes V,W, X, Y, Z and primary key V Y?
A
VXYZ
B
VWXZ
C
VWXY
D
VWXYZ
GATE CSE 2016 SET-1   Database Management System
Question 8
If D_1,D_2,...D_n are domains in a relational model, then the relation is a table, which is a subset of
A
D_{1} \oplus D_{2} \oplus \cdots \oplus D_{n}
B
D_{1} \times D_{2} \times \cdots \times D_{n}
C
D_{1} \cup D_{2} \cup \cdots \cup D_{n}
D
D_{1} \cap D_{2} \cap \cdots \cap D_{n}
ISRO CSE 2015   Database Management System
Question 9
Let R=(A,B,C,D,E,F) be a relation scheme with the following dependencies C \rightarrow F, E \rightarrow A, EC \rightarrow D, A \rightarrow B. Which of the following is a key of R?
A
CD
B
EC
C
AE
D
AC
ISRO CSE 2015   Database Management System
Question 10
The maximum length of an attribute of type text is
A
127
B
255
C
256
D
It is variable
ISRO CSE 2015   Database Management System
There are 10 questions to complete.

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