For correct behaviour during recovery, undo and redo operation must be
Commutative
Associative
idempotent
distributive
Correct Answer :
C. idempotent
Related Questions
The rule that a value of a foreign key must appear as a value of some specific table is called a
Referential constraint.
Index.
Integrity constraint.
Functional dependency.
DBMS is a collection of _____ that enables user to create and maintain a database.
Keys
Program
Translators
Language Activity
Grant and revoke are _____ statements.
TCL
DCL
DDL
DML
Checkpoints are a part of
Recovery measures.
Security measures.
Concurrency measures.
uthorization measures.
According to the levels of abstraction, the schema at the intermediate level is called
Logical schema.
Physical schema.
Subschema.
None of the above.
………………… approach reduces time and effort required for design and lesser risk in database management.
Single global database
Multiple databases
Top-down approach
None of the above
Which two files are used during operation of the DBMS?
Query languages and utilities
DML and query language
Data dictionary and transaction log
Data dictionary and query language
Data items grouped together for storage purposes are called a
record
string
title
list
An outstanding functionality of SQL is its support for automatic_____ to the target data.
programming
navigation
functioning
notification
______is a preferred method for enforcing data integrity
Constraints
Triggers
Stored procedure
Cursors
The normal form that is not necessarily dependency preserving is
2NF
3NF
BCNF
4NF
Which of the following aggregate functions does not ignore nulls in its results?.
COUNT .
COUNT (*)
MAX
MIN
If two relations R and S are joined, then the non matching tuples of both R and S are ignored in
left outer join
right outer join
full outer join
inner join
Key to represent relationship between tables is called
primary key
secondary key
foreign key
none of the above
Which of the syntax is correct for insert statement?
i) insert into values
ii) insert into (column list) values
ii) insert into
i-only
ii-only
Both of them
None of them
In an ER diagram the ___shape specifies the Attibute and a ____ shape specifies the primary key attribute.
Oval; An oval with an underlined attribute
Circle; A circle with bolded attribute inside it
Diamond; A bolded attribute
Square; An attribute within the square
Processed data is called _____
Raw data
Source
Information
Useful data
The relational model is based on the concept that data is organized and stored in two-dimensional tables called ______
Fields
Records
Relations
Keys
The common column is eliminated in
theta join
outer join
natural join
composed join
Maximum height of a B+ tree of order m with n key values is
Logm(n)
(m+n)/2
Logm/2(m+n)
None of these
In an E-R, Y is the dominant entity and X is a subordinate entity. Then which of the following is incorrect :
Operationally, if Y is deleted, so is X
existence is dependent on Y.
Operationally, if X is deleted, so is Y.
Operationally, if X is deleted, & remains the same.
Shadow paging has
no redo
no undo
redo but no undo
neither redo nor undo
E-R Modeling is achieved by using ____ diagrams
DFD
Flowcharts
Gantt Charts
E-R
In b-tree the number of keys in each node is than the number of its children.
one less
same
one more
half
______ keyword is used to find the number of values in a column.
TOTAL
ADD
COUNT
SUM
The transactions like adding an employee, enrolling a student in a course are examples of _______
Logical
Physical
None
Theoretical
Between DRAM and magnetic disk storage another form of memory, called ______ memory is becoming common because it is non volatile.
RAM
Flash
Hard Disk
Secondary
Use of UNIQUE while defining an attribute of a table in SQL means that the attribute values are
distinct values
cannot have NULL
both (A) & (B)
same as primary key
Relational Algebra does not have
Selection operator.
Projection operator.
Aggregation operators.
Division operator.
Which of the following ensures the atomicity of the transaction?
Transaction management component of DBMS
Application Programmer
Concurrency control component of DBMS
Recovery management component of DBMS