Relational Schema


Question 1
Which one of the options given below refers to the degree (or arity) of a relation in relational database systems?
A
Number of attributes of its relation schema.
B
Number of tuples stored in the relation.
C
Number of entries in the relation.
D
Number of distinct domains of its relation schema.
GATE CSE 2023   Database Management System
Question 2
Consider a relation R( A, B, C, D, E ) with the following three functional dependencies.
AB \rightarrow C;BC \rightarrow D; C \rightarrow E;
The number of superkeys in the relation R is .
A
12
B
8
C
6
D
5
GATE CSE 2022   Database Management System


Question 3
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 4
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 5
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


There are 5 questions to complete.

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