Database Set 1 (30 mcqs)

1. In magnetic disk ________ stores information on a sector magnetically as reversals of the direction of magnetization of the magnetic material.
a) Read–write head
b) Read-assemble head
c) Head–disk assemblies
d) Disk arm

2. A __________ is the smallest unit of information that can be read from or written to the disk.
a) Track
b) Spindle
c) Sector
d) Platter

3. The disk platters mounted on a spindle and the heads mounted on a disk arm are together known as ___________.
a) Read-disk assemblies
b) Head–disk assemblies
c) Head-write assemblies
d) Read-read assemblies
View Answer

4. The disk controller uses ________ at each sector to ensure that the data is not corrupted on data retrieval.
a) Checksum
b) Unit drive
c) Read disk
d) Readsum

5. _________ is the time from when a read or write request is issued to when data transfer begins.
a) Access time
b) Average seek time
c) Seek time
d) Rotational latency time

6. The time for repositioning the arm is called the ________, and it increases with the distance that the arm must move.
a) Access time
b) Average seek time
c) Seek time
d) Rotational latency time

7. _________ is around one-half of the maximum seek time.
a) Access time
b) Average seek time
c) Seek time
d) Rotational latency time

8. Once the head has reached the desired track, the time spent waiting for the sector to be accessed to appear under the head is called the _______________.
a) Access time
b) Average seek time
c) Seek time
d) Rotational latency time

9. In Flash memory, the erase operation can be performed on a number of pages, called an _______, at once, and takes about 1 to 2 milliseconds.
a) Delete block
b) Erase block
c) Flash block
d) Read block

10. Hybrid disk drives are hard-disk systems that combine magnetic storage with a smaller amount of flash memory, which is used as a cache for frequently accessed data.
a) Hybrid drivers
b) Disk drivers
c) Hybrid disk drivers
d) All of the mentioned

11.
Name
Annie
Bob
Callie
Derek
Which of these query will display the the table given above ?
a) Select employee from name
b) Select name
c) Select name from employee
d) Select employee

12. Select ________ dept_name
from instructor;
Here which of the following displays the unique values of the column ?
a) All
b) From
c) Distinct
d) Name

13. The ______ clause allows us to select only those rows in the result relation of the ____ clause that satisfy a specified predicate.
a) Where, from
b) From, select
c) Select, from
d) From, where

14. Select ID, name, dept name, salary * 1.1
where instructor;
The query given below will not give an error. Which one of the following has to be replaced to get the desired output?
a) Salary*1.1
b) ID
c) Where
d) Instructor

15. The ________ clause is used to list the attributes desired in the result of a query.
a) Where
b) Select
c) From
d) Distinct

16. Select name, course_id
from instructor, teaches
where instructor_ID= teaches_ID;
This Query can be replaced by which one of the following ?
a) Select name,course_id from teaches,instructor where instructor_id=course_id;
b) Select name, course_id from instructor natural join teaches;
c) Select name ,course_id from instructor;
d) Select course_id from instructor join teaches;

17. Select * from employee where salary>10000 and dept_id=101;
Which of the following fields are displayed as output?
a) Salary, dept_id
b) Employee
c) Salary
d) All the field of employee relation

18.
Employee_id    Name    Salary
1001    Annie    6000
1009    Ross    4500
1018    Zeith    7000
This is Employee table.
Select * from employee where employee_id>1009;
Which of the following employee_id will be displayed?
a) 1009, 1001, 1018
b) 1009, 1018
c) 1001
d) 1018

19. Which of the following statements contains an error?
A) Select * from emp where empid = 10003;
B) Select empid from emp where empid = 10006;
C) Select empid from emp;
D) Select empid where empid = 1009 and lastname = ‘GELLER’;

20. Insert into employee _____ (1002,Joey,2000);
In the given query which of the keyword has to be inserted ?
a) Table
b) Values
c) Relation
d) Field

21. A _____ indicates an absent value that may exist but be unknown or that may not exist at all.
a) Empty tuple
b) New value
c) Null value
d) Old value

22. If the attribute phone number is included in the relation all the values need not be entered into thephone number column . This type of entry is given as
a) 0
b) –
c) Null
d) Empty space

23. The predicate in a where clause can involve Boolean operations such as and.The result of true and unknown is_______, false and unknown is _____, while unknown and unknown is _____.
a) Unknown, unknown, false
b) True, false, unknown
c) True, unknown, unknown
d) Unknown, false, unknown

24. Select name
from instructor
where salary is not null;
Selects
a) Tuples with null value
b) Tuples with no null values
c) Tuples with any salary
d) All of the mentioned

25. In a employee table to include the attributes whose value always have some value which of the following constraint must be used ?
a) Null
b) Not null
c) Unique
d) Distinct

26. Using the ______ clause retains only one copy of such identical tuples.
a) Null
b) Unique
c) Not null
d) Distinct

27. Create table employee (id integer,name varchar(20),salary not null);
Insert into employee values (1005,Rach,0);
Insert into employee values (1007,Ross, );
Insert into employee values (1002,Joey,335);
Some of these insert statements will produce an error. Identify the statement.
a) Insert into employee values (1005,Rach,0);
b) Insert into employee values (1002,Joey,335);
c) Insert into employee values (1007,Ross, );
d) Both a and c

28. The primary key must be
a) Unique
b) Not null
c) Both a and b
d) Either a or b

29. You attempt to query the database with this command: (25)
select nvl (100 / quantity, none)
from inventory;
Why does this statement cause an error when QUANTITY values are null?
a. The expression attempts to divide by a null value.
b. The data types in the conversion function are incompatible.
c. The character string none should be enclosed in single quotes (‘ ‘).
d. A null value used in an expression cannot be converted to an actual value

30. The result of _____unknown is unknown.
a) Xor
b) Or
c) And
d) Not

Answers
1-d 2-c 3-b 4-a 5-a
6-c 7-b 8-d 9-b 10-b
11-c 12-c 13-a 14-c 15-b
16-d 17-d 18-d 19-d 20-b
21-c 22-c 23-d 24-b 25-b
26-b 27-c 28-c 29-a 30-d

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