Brief Questions
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COMPUTER : DBMS ( DATABASE MANAGEMENT
SYSTEM )
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What is Database?
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A database is a
collection of information that is organized so that it can easily be
accessed, managed and updated.
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What is Database
Management System?
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DBMS is a software
package designed to define, manipulate, retrieve and manage data in a
database. It defines rules for validating and manipulating that data. Fourth
generation query languages like SQL are used along with DBMS package to
interact with database.
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Some of the real time
applications using DBMS are Banking (transactions), Airlines (reservations
and schedules), Universities (registration and grades), Manufacturing
(production, inventory, orders, supply chain) etc.
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Advantages of a
DBMS
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Controls
Data Redundancy: All of the data is integrated into a single centralized file
and no duplicates are created.
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Data
Sharing: Database administrator upon granting access allows for
sharing of data across different platforms and different users.
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Data
consistency: As a data item appears only once, update has to be done once
only and updated value is immediately available for use.
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Integration
of Data: In DBMS, data is stored in tabular form and various
relationships can be created among tables. This makes it easy to retrieve and
update data.
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Data
Security: The access to critical information can be restricted and
access privileges are required for updating/manipulating important
information. E.g.-access to financial data is restricted providing for
security of data.
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Backup
and Recovery: It has subsystems which deal with back up and recovery in
case of hardware/software failure or in case of a natural calamity which
endangers the data in any way.
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Concurrent
Access: It provides for concurrent access to multiple users at one
time making it more efficient for business applications.
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Components of DBMS
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A database system
consists of 4 components usually:
Data
Hardware
Software
Users
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1.
Data: It is the most important component of a database which acts
like a bridge between hardware and software. Different types of data are-
User data (actual/workable data stored in tables), Metadata ( data about data
i.e no of tables, no of fields), application metadata (structure and format
of queries)
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2.
Hardware: Storage devices on which data is stored with i/o operations
(hard disks, optical disks, magnetic tapes etc)
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3.
Software: It acts a bridge between user and database. It interacts with
both user and database and acts a medium for data exchange. For performing
various operations on the data, we use query languages like SQL etc.
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4.
Users: They are the ones who need information from a database to
carry out their primary business responsibilities. Various types of users
are: Database administrators, Database designers, End users, Application
Programmers.
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Levels of
Abstraction
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1.
Physical Level
It describes how a record (e.g. customer) is stored in the database.
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2.
Logical Level
It describes the data stored in database and the relationships among
themselves. Lets look at the description of customer data below:
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cust_id: int;
cust_name: string;
cust city: string;
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3. View Level
At this level, application programs hide details of data types. Views can
also hide information such as employee salary for security purposes.
Database Management System
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