What are the different types of radio waves that are used for computer network applications?
i) Spread spectrum
ii) High power, single frequency
iii) High power, multiple frequency
iv) Low power, single frequency
v) Low power, multiple frequency
i, ii and iii only
i, ii and iv only
ii, iii and iv only
i, iii and iv only
Correct Answer :
B. i, ii and iv only
Related Questions
An association of several structure of a data base can be expressed graphically by?
Tuple
Record
Relationship
Field
Which of the following file organization provides very fast access to any arbitrary record of a file?
Ordered file
Unordered file
Hashed file
B-tree
Specialization is a
top-down approach.
bottom-up approach.
left-right approach.
none of the above
An entity set that does not have sufficient attributes to form a primary key is a
strong entity set.
weak entity set.
simple entity set.
primary entity set.
A functional dependency between two or more non-key attributes is called
Transitive dependency
Partial transitive dependency
Functional dependency
Partial functional dependency
The language used in application programs to request data from the DBMS is referred to as the
DML
DDL
VDL
SDL
Which of the following operator preserves unmatched rows of the relations being joined?
Inner join
Outer join
union
Intersect
Which of the following are the properties of entities?
Groups
Table
Attributes
Switchboards
What is the result of the following SQL statement ?
SELECT A.emp_Name, B.ph_num
FROM emp A LEFT OUTER JOIN phone B
ON A. emp_ID = B.emp_ID
A list of employees phone number
A list of all employees that have spouses, with phone number included in the list
A list of all employees names, including the phone number if they have one
Two lists : One list of employees, the other of phone numbers
The overall design of a database is called
Subschema of the database
Schema of the database
Structure of the database
View of the database
In two-phase locking
the data items are locked in growing phase.
the data items are released in shrinking phase.
Both A and B are true
Both A and B are false
Expand the acronym OLAP
Object Linked Access Program
Organizational Architecture Processing
Online Analytical Processing
none of these
Select the incorrect statement
BCNF is stronger than 3NF
Relational algebra is a non-procedural language
Every conflict serializable schedule is view serializable.
none of the above
The exists construct returns the value true, if the argument subquery is
empty
nonempty
contains null values
none of the above
The syntax to select all column from the table is
select all from tablename
select * from tablename
select from tablename
none of these
The transaction consists of all statements executed between
the begin transaction and end transaction
the start transaction and end transaction
the begin transaction and finish transaction
none of the above.
In a Hierarchical model records are organized as
Graph.
List.
Links.
Tree.
Data integrity refers to
the uniqueness of the data in a database
the correctness and completeness of the data in a database
the un redundancies of the data in a database
Data independence of the database
B-Tree is used for
searching data
storing data
both A and B
none of these
A lock that allows concurrent transactions to access different rows of the same table is known as a
Field-level lock
Row-level lock
Table-level lock
Database-level lock
Radio frequencies below ............. are more suitable for omnidirectional applications.
300MHz
1GHz
5GHz
10 GHz
A type of query that is placed within a WHERE or HAVING clause of another query is called
Super query
Sub query
Master query
Multi-query
For large networks, _______ topology is used
Ring
Bus
Mesh
none of these
What does a field or a combination of fields that has a unique value called ?
Foreign key
Secondary key
Primary key
Alternate key
Referential integrity
controls relationships between operations of an object
controls relationships between instances of a class
controls relationships between attributes in a table
controls relationships between tables in a database
The types of noiseless channels are
i) Selective Reject ARQ
ii) simplest protocol
iii) Go-Back-N ARQ
iv) Stop-and-Wait Protocol
i, ii only
ii and iv only
ii and iv only
i, iv only
Which of the following produces the relation that has attributes of R1 and R2
Cartesian product
Difference
Intersection
Product
In E-R Diagram weak entity set are represented by
Ellipse
Dashed ellipse
Dashed Rectangle
Doubled Rectangle
In an object oriented model, one object can access data of another object by passing?
Instance variable
Variable
Message
Function
In case of entity integrity, the primary key may be
not Null
Null
both Null & not Null.
any value.