1)What is database?
A database is a logically coherent collection of data
with some inherent meaning, representing some aspect of real world and which is
designed, built and populated with data for a specific purpose.
2)What is a Database system?
The database and DBMS software together is called as
Database system.
3)What is DBMS?
It is a collection of programs that enables user to
create and maintain a database. In other words it is general-purpose software
that provides the users with the processes of defining, constructing and
manipulating the database for various applications.
4) What are the advantages of DBMS?
Redundancy is controlled.
Unauthorised
access is restricted.
Providing
multiple user interfaces.
Enforcing
integrity constraints.
Providing
backup and recovery.
5)Describe the three levels of data
abstraction?
Physical level:
The lowest level of abstraction describes how data are stored.
Logical level:
The next higher level of abstraction, describes what data are stored in
database and what relationship among those data.
View level: The
highest level of abstraction describes only part of entire database.
6)What is Data Model?
A collection of conceptual tools for describing data,
data relationships data semantics and constraints.
7)What is E-R model?
This data model is based on real world that consists of
basic objects called entities and of
relationship among these objects. Entities are described in a database by a set
of attributes.
8)What is Object Oriented model?
This model is based on collection of objects. An object
contains values stored in instance variables with in the object. An object also
contains bodies of code that operate on the object. These bodies of code are
called methods. Objects that contain same types of values and the same methods
are grouped together into classes.
9) What is DML (Data Manipulation Language)?
This language that enable user to access or manipulate
data as organised by appropriate data
model. Procedural DML or Low level: DML requires a user to specify what data
are needed and how to get those data. Non-Procedural DML or High level: DML
requires a user to specify what data are needed without specifying how to get those data
10)What is DML Compiler?
It translates DML statements in a query language into
low-level instruction that the query evaluation engine can understand.
11)What is an attribute?
It is a particular property, which describes the entity.
12) What is RDBMS?
Relational Data Base Management Systems (RDBMS) are
database management systems that maintain data records and indices in tables.
13)What’s difference between DBMS and RDBMS?
DBMS provides a systematic and organized way of storing,
managing and retrieving from collection of logically related information. RDBMS
also provides what DBMS provides but above that it provides relationship
integrity.
14)What is SQL?
SQL stands for Structured Query Language. SQL is an ANSI
(American National Standards Institute) standard computer language for
accessing and manipulating database systems. SQL statements are used to
retrieve and update data in a database.
15)What is Stored Procedure?
A stored procedure is a named group of SQL statements
that have been previously created and stored in the server database.
16) What do you mean by atomicity and
aggregation?
Atomicity-Atomicity states that database modifications
must follow an “all or nothing” rule. Each transaction is said to be “atomic.”
If one part of the transaction fails,
the entire transaction fails.
Aggregation - A feature of the entity relationship model
that allows a relationship set to participate in another relationship set. This
is indicated on an ER diagram by drawing a dashed box around the aggregation.
17) Disadvantage in File Processing System?
Data redundancy
& inconsistency.
Difficult in
accessing data.
Data isolation.
Data integrity.
Concurrent
access is not possible.
Security
Problems.
18)What is VDL (View Definition Language)?
It specifies user views and their mappings to the
conceptual schema.
19)What is SDL (Storage Definition Language)?
This language is to specify the internal schema. This
language may Specify the mapping between two schemas.
20)Describe the difference between homogeneous and
heterogeneous distributed database?
A homogenous database is one that uses the same DBMS at
each node. A heterogeneous database is one that may have a different DBMS at
each node.
21)What is a distributed database?
A distributed database is a single logical database that
is spread across more than one node or locations that are all connected via
some communication link.
22) Explain the difference between two and
three-tier architectures?
Three-tier architecture includes a client and two server
layers.
The application
code is stored on the application server and the database is stored on the database server. A two-tier
architecture includes a client and one server layer. The database is stored on
the database server.
23)Briefly describe the three types of SQL
commands?
Data definition language commands are used to create,
alter, and drop tables. Data manipulation commands are used to insert, modify,
update, and query data in the database. Data control language commands help the
DBA to control the database.
24) List some of the properties of a relation?
List some of the
properties of a relation?
Relations in a database have a unique name and no
multivalued attributes exist. Each row is unique and each attribute within a
relation has a unique name. The sequence of both columns and rows is
irrelevant.
25)Explain the differences between an intranet
and an extranet?
An Internet database is accessible by everyone who has
access to a Web site. An intranet database limits access to only people within
a given organization.