Key Concepts GATE CS PYQ Quiz

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Question 1

Consider a relational table with a single record for each registered student with the following attributes.

1. Registration_Num: Unique registration number
   of each registered student
2. UID: Unique identity number, unique at the 
   national level for each citizen
3. BankAccount_Num: Unique account number at
   the bank. A student can have multiple accounts
   or join accounts. This attribute stores the 
   primary account number.
4. Name: Name of the student
5. Hostel_Room: Room number of the hostel

Which one of the following option is INCORRECT?

BankAccount_Num is candidate key
Registration_Num can be a primary key
UID is candidate key if all students are from the same country
If S is a superkey such that S∩UID is NULL then S∪UID is also a superkey

Question 2

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?

Both S1 and S2 are true
S1 is true and S2 is false
S1 is false and S2 is true
Both S1 and S2 are false

Question 3

The maximum number of superkeys for the relation schema R(E,F,G,H) with E as the key is

Question 4

Consider a relation scheme R = (A, B, C, D, E, H) on which the following functional dependencies hold: {A–>B, BC–>D, E–>C, D–>A}. What are the candidate keys of R?

AE, BE
AE, BE, DE
AEH, BEH, BCH
AEH, BEH, DEH

Question 5

Given the following statements:

    S1: A foreign key declaration can always 
        be replaced by an equivalent check
        assertion in SQL.
    S2: Given the table R(a,b,c) where a and
        b together form the primary key, the 
        following is a valid table definition.
        CREATE TABLE S (
            a INTEGER,
            d INTEGER,
            e INTEGER,
            PRIMARY KEY (d),
            FOREIGN KEY (a) references R)

Which one of the following statements is CORRECT?

S1 is TRUE and S2 is FALSE.
Both S1 and S2 are TRUE.
S1 is FALSE and S2 is TRUE.
Both S1 and S2 are FALSE.

Question 6

The following table has two attributes A and C where A is the primary key and C is the foreign key referencing A with on-delete cascade.

The set of all tuples that must be additionally deleted to preserve referential integrity when the tuple (2,4) is deleted is:

(3,4) and (6,4)
(5,2) and (7,2)
(5,2), (7,2) and (9,5)
(3,4), (4,3) and (6,4)

Question 7

A prime attribute of a relation scheme R is an attribute that appears

in all candidate keys of R.
in some candidate key of R.
in a foreign key of R.
only in the primary key of R.

Question 8

Consider a relation R(A, B, C, D, E,) with the following three functional dependencies.

AB->C; BC->D; C->E
The number of super keys in the relation R is______

Question 9

An index is clustered, if

It is on a set of fields that form a candidate key.
It is on a set of fields that include the primary key.
The data records of the file are organized in the same order as the data entries of the index.
The data records of the file are organized not in the same order as the data entries of the index.

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DBMS

GATE CS

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