The union of primary keys of a related entity becomes …………. Of a relation.
primarykey
superkey
candidatekey
foreignkey
Correct Answer :
B. superkey
Related Questions
In defining the notion of the tuple variable, which one of the clause is useful?
as
by
from
none of the above
An operation that will increase the length of a list is
insert
modify
lookup
none of the above
Data fragmentation is performed by the …… and each fragment is stored at…………..
DBMS, same site
OS ,same site
DBMS ,different site
OS ,different site
A transaction has following states
i) Active
ii) Fail
iii) Abort
iv) Commit
i and ii only
ii and iii only
i and iii only
iii and iv only
DBMS utility which allows to reconstruct the correct state of database from the backup and history of transactions
Backup
Recovery
Grant
Troubleshooting
A logical description of some portion of database that is required by a user to perform task is called as
System View
User View
Logical View
Data View
In which of the random-access method, stations do not sense the medium?
ALOHA
ETHERNET
CSMA/CA
CSMA/CD
The physical path over which a message travels
Thermal
Medium
Protocol
Impulse
A logical schema
is the entire database.
is a standard way of organizing information into accessible parts.
describes how data is actually stored on disk.
both A) and C)
Which of the following is not a database object?
index
sequence
cursor
trigger
Which of the following is the unit of signaling speed or modulation rate or the rate of symbol transmission?
Data rate
Bit rate
Signal to Noise Ratio
Baud rate
B-Tree is used for
searching data
storing data
both A and B
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
The index table has …… Columns.
1
2
3
4
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
Commit operation …………… writes the changes made to the database.
temporarily
permanently
none of these
all of the above
In ………… paging we make copy of the current page table.
physical
logical
shadow
duplicate
By default a user who has been granted some form of authorization
is allowed to pass them to others
is not allowed to pass them to others
may be or may not be allowed to pass them to others
none
The ________ states that a foreign key must either match a primary key value in another relation or it must be null.
entity integrity rule
referential integrity constraint
composite attribute
action assertion
The method of access which uses key transformation is known as
direct.
hash.
random.
sequential.
Noisy channel has ……… .. types of protocols
two
three
four
none
Only one communication channel is needed rather than n channels to transmit data between two communicating devices
parallel
serial
analog
digital
File organization that provides fast access to any arbitrary record
Hashed file
B-tree
Ordered file
Unordered file
It is possible to define a schema completely using
VDL and DDL.
DDL and DML.
SDL and DDL.
VDL and DML.
Datalog is
procedural query language
nonprocedural query language
scan(), write()
none of the above
Which of the following layer uses trailer of the frame for error detection?
Transport layer
Network layer
Datalink layer
None of these
............... noise is caused by the random motion of the electrons in a wire and is avoidable.
Thermal
Intermodulation
Cross talk
Impulse
The ability to modify the conceptual schema without causing any change to the application program is known as
Physical data independence
Logical data independence
External data independence
Static data
In E-R Diagram weak entity set are represented by
Ellipse
Dashed ellipse
Dashed Rectangle
Doubled Rectangle
Which command is used to cancel privileges granted through the GRANT command ?
CANCEL
OVER
STOP
REVOKE