DBMS topic in PU

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Database :-

A Database is a structure that can store information about multiple types of entities ,and the relationships among the entities .

Entity :-

An entity is a person , place, object or idea for which you want to store and process data.

Attribute:-

An Attribute is a characteristic or property of an entity.

The term used in this text exactly as it is used.

Data Base Management System :-

A DBMS is a program or a collection of programs , though which users interact with a database . The actual manipulation of the underlying in handled by the DBMS .

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Database application:-

An application program (or set of related programs)that is used to perform a series of database activities (Create, read,

update and delete) on behalf of database users. Each database application performs some combination of the following basic operation

1)Create :- Add new data to the database.

2)Read :- Read current database data (often presented in a useful format on a computer screen or on a printed report).

3)Update :- Update or modify current data.

4)Delete :- Delete current data from the database.

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DBMS Advantages

DBMS has many advantages such as:

Reduction in data Redundancy :-

It means that DBMS helps in removing duplicate data from the database. It will notice that Redundancy leads to several problems:

i) Duplication of Efforts .

ii) Save the storage space /memory where data is saved.

Provides Security :-

Restrict users to access all the information of the database by providing passwords and rights .there are also various coding techniques to maintain the security of important and crucial information from unauthorized users and accidents.

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DBMS Advantages

Data can be shared among various users:-

In a database system , data can be easily shared by different users .For example ,student data can shared by teacher department subject wise ,Fee department ,library etc.

Data Integrity :-

since a large number of users can access database together at the same time . So, to maintain the same data/information correct every time and at every place during any operation is called data integrity.

Maintenance of data integrity :-

data Integration can be understood by the fact that data contained in the database should be accurate and consistent.

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Types of DBMS Models

These categories are made on the basis of the ways in which data are stored in the database :

1)Flat file or sequential .

2)Hierarchical

3)Network

4)Relational

5)Entity–relationship model

6)Object database

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Sequential or Flat File

Flat File:-

A Flat File can be defined as a text file in which you can organize the data in your own format and it is not linked with any other file .In this the data is processed in the way the data is stored.

Example:-MS Spread Sheet.

Item name Price Quantity Store Name

Date of sale

Bread 15 5 saravana 30-08-2014

Butter 46 6 saravana 30-08-2014

Biscuits 56 8 saravana 01-09-2014

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Sequential or Flat File

Advantages of Flat File System:-

1) It is simple and easy to implement.

2) It can be used for small database

3) It is used where no links between data or files are required.

Disadvantage of File System :-

1)Duplication of data Entries.

2)Since the access mode is sequential or in a single order, the system gets slower for large database.

3)The file is hard to recover if it is corrupted or system crashes .

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Hierarchical Database Model

• In this kind of database, data are stored in the form of a hierarchy .Hierarchy

database is like a tree structure which has one root and many branches .It uses the

concept of parent child relation ship .in this type of database a single file may have

many relationship.

this system is very advance compare to sequential system(a flat file).

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Hierarchical Database Model 10

Hierarchical Database Model

Advantages of Hierarchical databases :- it is having following advantage

1) Hierarchical model is simple to construct.

2)This type of database is generally used in daily life organizations where data is organized in hierarchically organized domains, component assemblies in manufacturing ,personnel organization in companies.

3)Accessing of data is faster in hierarchical database compared to sequential database.

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Hierarchical Database Model

Disadvantages of Hierarchical Database :-

1) Complex implementation

2)Difficult to manage

3)Lacks structural independence

4)Complex applications programming and use

5)Implementation limitations

6)Lack of standards

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Network database model

• In this model, a parent can have many children and a child can also have many parent records. These records are physically linked through linked lists.

network model was developed in mid 1960s as part of work of CODASYL(Conference on Data Systems Languages) which proposed programming language COBOL(1966) and then network model(1971).

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Network database model 14

Network database model

Advantages of network Model:-

1)It eliminates unnecessary duplication of data with associated errors and costs.

2)It uses concept of a data definition language ,data manipulation language .

3)It uses concept of m:n linkages or relationships, which mean that an owner record can have many members records. Similarly a member record can have several owners .but a hierarchical model allows only 1:n

Disadvantages of network Model :-

1)System complexity

2)Lack of structural independence

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Relational data model :-In this model of DBMS ,data is stored in two- dimensional table (rows, and columns ),this is a model relation between two tables exists with something in common or some data which these two tables share. Each column of a table is referred ta as an attribute and the values which it may contain is called domain of values.

In this model was proposed by IBM researcher E.F.Codd in 1970. it is more of a concept than a data structure varies substantially from one RDBMS to another .Relational database model use relational concept of mathematics in a table .

You can understand Relational Model where

Each row is a record or tuple.

Each column is an attribute.

Primary Key:-

the Primary Key of a table uniquely identifies the record .

Foreign Key :-

The Foreign key is the key of a table which is used for referencing the other table .

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Relational data model :-• Example :1 Student table and its primary Key

ID No(Primary Key)

Student Name Class Department

S34877 Raja Sekhar MLIS Library and Information Science

S34878 Avani MSc Computer Science

S34879 Kadiresan MLIS Library and information science

S34880 Amees MLIS Library and information science

S34881 Gopi MA English

S34882 Shyndeep MLIS Library and information science

S34883 Rajesh MBA Business Management

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Relational data model :-

• Example :- Library Table

Book No (Primary Key)

ID No(Foreign Key)

Title Issued Date

12567 S34877 Colon classification 26/09/2014

15498 S34878 Database System 16/09/2014

12578 S34879 Information Resources 22/092014

12576 S34880 MARC21 14/092014

14582 S34881 William Shakespeare 24/09/2014

12565 S34882 Library Associations 22/09/2014

14825 S34883 Business Law 15/09/2014

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Relational data model :-Advantages of Relational data Model:-1)Structural independence.

2)Improved conceptual simplicity.

3)Easier database design, implementation, management, and use.

4)Ad hoc query capability.

5)Powerful database management system.

Advantages of Relational data Model:-1)Substantial hardware and system software overhead.

2)Can facilitate poor design and implementation

3)May promote “islands of information "problems

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Entity Relationship Models

Entity- relationship model is a logical representation of data for an organization or for a business area .the E-R model consists of entities which have attributes and relationships between these entities .

E-R model was proposed by peter in 1976. simply stated ,the ER model is a conceptual data model that views the real world as entities and relationships.

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Entity Relationship Models 21

Entity Relationship Models

Advantages of Entity Relationship Models:-1)Exceptional conceptual simplicity

2)Visual representation

3)Effective communication tool

4)Integrated with the relational data model.

Disadvantages of Entity Relationship Models:-

1)Limited constraint representation

2)Limited relationship representation

3)No data manipulation language

4)Loss of information content

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Object Oriented Model

An object database (also object-oriented database management system) is a database management system in which information is represented in the form of objects as used in object-oriented programming. Object databases are different from relational databases which are table-oriented.

•Object is described by its factual content

•Includes information about relationships between facts within object and relationships with other objects.

•Subsequent OODM development allowed an object to also contain operations

••Object becomes basic building block for autonomous structures

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Object Oriented Model

Basic structure of OODB model:-Object: abstraction of a real-world entity.

Attributes describe the properties of an object.

Objects that share similar characteristics are grouped in classes.

Classes are organized in a class hierarchy.

Inheritance is the ability of an object within the class hierarchy to inherit the attributes and methods of classes above it.

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Object Oriented Model 25

Object Oriented Model

Advantages of OODBMS model:-1)Object model intuitively closer to real world

2)Extensibility – inheritance

3)Complex values

4)Removal of impedance mismatch

5)More expressive query language

6)Tight coupling between data and applications allows schema

to capture more of the meaning of applications

7) Support for long transactions

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Object Oriented Model

Advantages of OODBMS model:-8) Better support for applications like software engineering or

computer aided design (CAD)

9) Arguably better performance, though benchmarks have mainly

been applied in areas like engineering support to which OODBMS

are better suited.

Disadvantages of OODBMS model:-1) Lack of a theoretical foundation, so exact meaning of OODM

is not well defined (though this is mitigated by the ODMG model)

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Object Oriented Model

Disadvantages of OODBMS model:-2)More difficult to get staff experienced with OODBMSs

3)Lack of standards (mitigated by ODMG's OQL)

4)Competition from relational and object-relational DBMS's

5)Encapsulation compromised to optimize queries (but in RDBMS's,

normalization may be compromised to improve performance).

6) OODBMS's usually control concurrency by locking; locking

an inheritance hierarchy is difficult and may affect performance.

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Object Oriented Model

7) OODM is inherently more complex than relational data model;

OODBMS provides more complex functionality than RDBMS;

complexity leads to higher implementation and maintenance costs.

8) Lack of views; but are views necessary with an object model?

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References :-

1)IGNOU computer fundamentals book.

2)Modern Database Management sixth edition.

3)Internet .

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Thank you

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