Database Management System Set 12

Database Management Systems

Questions 111 to 120


111.
Which of the following SQL aggregate function gives the number of rows containing not null values for the given column?
(a)
MIN
(b)
COUNT
(c)
MAX
(d)
SUM
(e)
AVG.
112.
“One disadvantage of index schemes in file organizations is that an index must be accessed and read to locate records.  In order to eliminate the need for maintaining and searching indexes, the method can be used as a method of direct record addressing.”
Find the appropriate option which fills in the blanks with suitable terms for (i) and (ii).
(a)
i.     sequential
ii.     indexing
(b)
i.     indexed Sequential
ii.     hashing
(c)
i.     sequential
ii.     hashing
(d)
i.     indexed Sequential
ii.     storage
(e)
i.     sequential
ii.     storage.
113.
A Relational operator that yields all possible pairs of rows from two tables is known as a/an
(a)
Union
(b)
Intersect
(c)
Difference
(d)
Project
(e)
Product.
114.
The following are the three language components of a database management system (DBMS).
I.     Data Definition Language (DDL).
II.     Sub-schema DDL.
III.    Data Manipulation Language (DML).
Two different types of people (users and practioners) are concerned with them. Which of them do users of a DBMS usually deal with?
(a)
Only (I) above
(b)
Only (III) above
(c)
Both (I) and (II) above
(d)
Both (II) and (III) above
(e)
All (I), (II) and (III) above.
115.
In the ANSI/SPARC three level database model, the external view is best described by which of the following options?
(a)
It is the link between users and the storage structures
(b)
It is dependent on the underlying DBMS product used (e.g. Oracle, DBASE)
(c)
It is the place where the users interface to the DBMS
(d)
It is not part of the model
(e)
It is the place where the storage structures link to the database.
116.
Match each term in Column A with the most appropriate definition in Column B.
Column A
Column B
(P)   Technological feasibility
(i)    Needs information from the database to carry out the primary business responsibility
(Q)   User
(ii)    Responsible for the database system and its associated application software
(R)   Practitioner
(iii)   Determines hardware and software availability for database system
(S)   Operational feasibility
(iv)   Determines availability of expertise and personnel needed for the database system

(a)
(P)→(iii), (Q)→(i), (R)→(ii), (S)→(iv)
(b)
(P)→(iv), (Q)→(i), (R)→(ii), (S)→(iii)
(c)
(P)→(iii), (Q)→(ii), (R)→(i), (S)→(iv)
(d)
(P)→(iv), (Q)→(ii), (R)→(i), (S)→(iii)
(e)
(P)→(ii), (Q)→(i), (R)→(iii), (S)→(iv).
117.
Which of the following set of operations represent a complete set of relational algebra operations?
(a)
{ σ, π, U}
(b)
{ ÷ , x }
(c)
{ σ, π, }
(d)
{π , , x}
(e)
{ – , x }.
118.
The following output is to be generated:
Fname
Minit
Ssn
Sex
Salary
SupperSsn
Dno
Sunil
T
334555
M
40000
88866
5
Amila
S
987615
F
43000
54321
4
Mahepala
K
668445
M
38000
33455
5
Which of the following would produce the above output?
(a)
s Employee (Dno = 4 AND Salary > 30000) OR (Dno = 5 AND Salary > 30000)
(b)
sEmployee (Ssn > 30000) AND (Sex = ’M’)
(c)
p Employee U p Employee Fname, Minit, Ssn, Sex, SupperSsn, Dno Salary
(d)
sEmployeeU s Employee (Dno = 4 AND Salary > 30000) (Dno = 5 AND Salary > 30000)
(e)
p (Employee) Ç p (Employee) Fname, Minit, Ssn, Sex, SupperSsn, Dno Salary.
119.
The referential integrity rule requires that ________.
(a)
Every null foreign key value must reference an existing primary key value
(b)
An attribute have a corresponding value
(c)
You delete a row in one table whose primary key does not have a matching foreign key value in another table
(d)
Every non-null foreign key value reference an existing primary key value
(e)
Both (a) and (c) above.
120.
The lock that prevents the use of any tables in the database from one transaction while another transaction is being processed is
(a)
Database-level lock
(b)
Table-level lock
(c)
Page-level lock
(d)
Row-level lock
(e)
Field-level lock.


Answers



111.
Answer : (b)
Reason  :       Count function gives the number of rows containing not null values for the given column.
112.
Answer : (b)
Reason  :       (i) indexed Sequential (ii) hashing.
113.
Answer : (e)
Reason  :       product is the Relational operator that yields all possible pairs of rows from two tables.
114.
Answer : (b)
Reason  :       The users and practioners are concerned with only Data manipulation language component of DBMS.
115.
Answer : (c)
Reason  :       It is the place where the users interface to the DBMS.
116.
Answer : (a)
Reason  :       (P)→(iii), (Q)→(i), (R)→(ii), (S)→(iv)
117.
Answer : (a)
Reason  :       { σ, π, U } are the sets of operations which represent a complete set of relational algebra operations.
118.
Answer : (c)
Reason  :       π (Employee) U π Employee Fname, Minit, Ssn, Sex, SupperSsn, Dno Salary
119.
Answer : (d)
Reason  :       The basic requirement of referential integrity is that every non-null foreign key value reference an existing primary key value.
120.
Answer : (a)
Reason  :       Data base-level lock prevents the use of any tables in the database from one transaction while other transaction is being processed.

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