DBMS
Chapter 8
Introduction to Database Management System
The raw facts constitute data
Information is the processed or organized form of data. If data is not correct or accurate, the information
obtained by processing such data may not be correct.
A database is a collection of logically related data items stored in an organised manner.
The information stored in a database can be added, modified, deleted or displayed according to the
requirements of the user.
The software that is used to create, update and retrieve data is known as database management system
(DBMS). It facilitates planning and maintenance of the database for the user.
Some of the common examples of DBMS are MS Access, Open Office or LibreOffice Base, Oracle, Ingress,
MySQL
ADVANTAGES OF DBMS
• Organised Storage – The data in the database is stored in an organised manner, so that retrieval of the
required data is fast and accurate.
• Data Analysis – A database helps in analysis of data based on certain criteria. It is easy to find out maximum
or minimum value, average or mean using a database.
• Data Sharing – If the same data set is required for different applications then the database can be shared
with other applications. Hence using a database means making once and using it repeatedly for multiple
applications.
• Minimal Data Redundancy – When the same data field is required in several tables, then the data field might
get repeated in number of tables. This is called as data redundancy. This can be reduced by using DBMS
tools.
• Data Consistency – By minimising data redundancy, chances of inconsistent data being stored is reduced.
• Increases Efficiency – Since database tables are properly organised, saving, reading and searching data can
be carried out efficiently.
• Increases Accuracy – Since data redundancy and inconsistency can be minimised in a database, the data is
retrieved accurately from the database.
• Increases Validity – Properties of different data fields can be assigned when a database is planned. So
whether or not valid data is being entered can be checked at the data entry stage. This increases the validity
of the database.
• Security – Unauthorised access can be controlled by assigning passwords to the users. The data might be
translated in such a manner that unauthorised users are not able to read it. This is known as encryption.
Both these measures increase the security of the database.
, Data Models
A database can be designed in different ways depending on the data being stored.
This structure of database is known as data model .It describes the manner in which data will be stored
and retrieved.
A data model consists of components for describing the data, relationships among them and the
constraints that hold data.
Hierarchical Data Model
In this model the data is organized into a tree like structure.
The data is stored in the form of records. Each record consists of one parent record and many children.
A record is a collection of fields and its data values.
All these records are linked to each other at various levels, thereby forming a hierarchy.
Hierarchical Data Model Network Data Model
Network Data Model
In this model, multiple records are linked to same master file.
It is also considered as an inverted tree where master is present in the bottom of the tree and the
It shows Many to many relation
Relational Data Model
It is the most commonly used database model.
The Relational Database Model was proposed in 1970 by E. F. Codd.
Relational database model is the most common type of database model.
The data elements are stored in different tables made up of rows and columns.
The data in different tables are related through the use of common fields. So relations are set between
tables based on common fields. That is why this model is termed as relational database mode. This data
model is based on the principle of setting relationships between two or more tables of the same
database.
• Relational Database – A relational database is a collection of related tables.
Chapter 8
Introduction to Database Management System
The raw facts constitute data
Information is the processed or organized form of data. If data is not correct or accurate, the information
obtained by processing such data may not be correct.
A database is a collection of logically related data items stored in an organised manner.
The information stored in a database can be added, modified, deleted or displayed according to the
requirements of the user.
The software that is used to create, update and retrieve data is known as database management system
(DBMS). It facilitates planning and maintenance of the database for the user.
Some of the common examples of DBMS are MS Access, Open Office or LibreOffice Base, Oracle, Ingress,
MySQL
ADVANTAGES OF DBMS
• Organised Storage – The data in the database is stored in an organised manner, so that retrieval of the
required data is fast and accurate.
• Data Analysis – A database helps in analysis of data based on certain criteria. It is easy to find out maximum
or minimum value, average or mean using a database.
• Data Sharing – If the same data set is required for different applications then the database can be shared
with other applications. Hence using a database means making once and using it repeatedly for multiple
applications.
• Minimal Data Redundancy – When the same data field is required in several tables, then the data field might
get repeated in number of tables. This is called as data redundancy. This can be reduced by using DBMS
tools.
• Data Consistency – By minimising data redundancy, chances of inconsistent data being stored is reduced.
• Increases Efficiency – Since database tables are properly organised, saving, reading and searching data can
be carried out efficiently.
• Increases Accuracy – Since data redundancy and inconsistency can be minimised in a database, the data is
retrieved accurately from the database.
• Increases Validity – Properties of different data fields can be assigned when a database is planned. So
whether or not valid data is being entered can be checked at the data entry stage. This increases the validity
of the database.
• Security – Unauthorised access can be controlled by assigning passwords to the users. The data might be
translated in such a manner that unauthorised users are not able to read it. This is known as encryption.
Both these measures increase the security of the database.
, Data Models
A database can be designed in different ways depending on the data being stored.
This structure of database is known as data model .It describes the manner in which data will be stored
and retrieved.
A data model consists of components for describing the data, relationships among them and the
constraints that hold data.
Hierarchical Data Model
In this model the data is organized into a tree like structure.
The data is stored in the form of records. Each record consists of one parent record and many children.
A record is a collection of fields and its data values.
All these records are linked to each other at various levels, thereby forming a hierarchy.
Hierarchical Data Model Network Data Model
Network Data Model
In this model, multiple records are linked to same master file.
It is also considered as an inverted tree where master is present in the bottom of the tree and the
It shows Many to many relation
Relational Data Model
It is the most commonly used database model.
The Relational Database Model was proposed in 1970 by E. F. Codd.
Relational database model is the most common type of database model.
The data elements are stored in different tables made up of rows and columns.
The data in different tables are related through the use of common fields. So relations are set between
tables based on common fields. That is why this model is termed as relational database mode. This data
model is based on the principle of setting relationships between two or more tables of the same
database.
• Relational Database – A relational database is a collection of related tables.
