Which of the following is not a constraint on a single relation?
check
unique
not null
is duplicate
Correct Answer :
D. is duplicate
Related Questions
............... noise is caused by the random motion of the electrons in a wire and is avoidable.
Thermal
Intermodulation
Cross talk
Impulse
Data independence means
data is defined separately and not included in programs.
programs are not dependent on the physical attributes of data.
programs are not dependent on the logical attributes of data.
both B) and C).
The database environment has all of the following components except:
users.
separate files.
database.
database administrator.
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 degree of the table with 500 rows and 7 columns is
500
7
3500
none of these
The maximum number of children in a B-tree of order m is
m+1
m
m-1
m/2
Which of the following is/are error-free channel(s)
i) Noisy channel
ii) Noiseless channel
i only
ii only
Both
None of these
Specialization is a
top-down approach.
bottom-up approach.
left-right approach.
none of the above
A …………… is a memory area where data are processed.
view
trigger
cursor
none of the above
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
An advantage of the database management approach is
data is dependent on programs.
data redundancy increases.
data is integrated and can be accessed by multiple programs.
none of the above.
The union of primary keys of a related entity becomes …………. Of a relation.
primarykey
superkey
candidatekey
foreignkey
The raw facts and figures are:
Data
Data field
DBMS
DBASE
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
A transaction which completes successfully is called
Granted
Committed
Compensated
Accomplished
In RDBMS, Data is presented as a collection of
Relation
Table
Attribute
Entity
Select the incorrect statement(s)
i) Foreign key values can be left blank
ii) In SQL duplicates may be present
iii) Theta join operation doesnt remove duplicate columns.
iv) NULL value means string of blank characters.
i ,iii only
ii, iv only
iii, iv only
ii, iii, iv
Which of the following statement returns data to the host variables one at a time?
SELECT
RETURN
FETCH
GET
Authorization command in SQL
Allow
Access
Grant
none of the above
A transaction which may not complete its execution successfully is termed as
Failed
Aborted
Blocked
Finished
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
An association of several structure of a data base can be expressed graphically by?
Tuple
Record
Relationship
Field
The access protocol used by traditional Ethernet
CSMA/CA
CSMA/CD
CSMA
Token ring
A data manipulation command the combines the records from one or more tables is called
SELECT
PROJECT
JOIN
PRODUCT
Attenuation can be also expressed in decibel dB) and commonly used because.
i) Signal strengths often fall off logarithmically
ii) Cascade losses and gains can be calculated with simple additions and subtractions
i only
ii only
Both A and B
None of the above
Natural mask for a Class A network
255.0.0.0
255.255.0.0
255.255.255.0
none of these
The method by which the structure of the database is modified to eliminate hidden dependencies and replacing groups is
Normalization
Indexing
Enforcing referential integrity
Enforcing data integrity
B-Tree is used for
searching data
storing data
both A and B
none of these
Which of the following submit and execute query at run time?
Static SQL
Dynamic SQL
both
none of these
Three SQL, DDL, CREATE commands are
Schema, Base and Table
Schema, Table and View
Base, Table and Schema
Key, Base and Table