database management system by - merry patel · database management system by ... data redundancy...

Prepared By Meri Dedania (AITS)

Database Management System

byMeri DedaniaAssistant Professor

MCA department

Atmiya Institute of Technology & Science

Yogidham Gurukul

Rajkot


Chapter -1

Introduction


Database

File System


Disadvantages of File System

Data Redundancy and Inconsistency

Difficulty in accessing data

Data isolation

Integrity Problems

Atomicity Problems

Concurrent-access anomalies

Security Problems


Name Address

ABC Bhiwani

DEF Delhi

AccNo Name Address

1002 ABC Bhiwani1005 DEF Jaipur


Customer Information Saving Account



Name Address

DEF Delhi

ABC Bhiwani

AccNo Name Address

1005 DEF Jaipur

1002 ABC Bhiwani

Customer InformationSaving Information

Manager

Requirement

ApplicationPrograms

File System

(ProgramsWritten in CPascal etc.)

(Data Structure

File Handling)

Database(Information Storage

in Files Format)

Difficulty in accessing data


Program in CProgram in C Program in COBOL

#include <stdio.h>Main()

{

-----}

New Document

01 Reserve-rec.03 saving

05 accno PIC A(2)

--------

Data Isolation


Atomicity Problems

Bank Data Transaction

User A User B


Concurrent-access anomalies


Employee

Information

Security Problem


Data Model

Data Models are internal Structure of Database.

It is collection of conceptual tools for describing data , data

relationships , data semantics , and consistency constraints.

A data model provides a way to describe the design of a

database at the physical , logical and view level.

The data models can be classified in four categories.

Hierarchical database model :

This is a data model in which the data is

organized into a tree structure.

The structure allows representing

information using parent/child relationships.

each parent can have many children, but

each child has only one parent (also known

as a 1-to-many relationship).

All attributes of a specific record are listed

under an entity type.

http://en.wikipedia.org/wiki/Data_model

http://en.wikipedia.org/wiki/Tree_data_structure

Network Data Model

The network model organizes data using

two fundamental concepts, called records

and sets.

Records contain fields.

Sets define one-to-many relationships

between records: one owner, many

members.

A record may be an owner in any number

of sets, and a member in any number of

sets.

http://en.wikipedia.org/wiki/Network_database

http://en.wikipedia.org/wiki/One-to-many






1. Relational Data Model : Using Collection of tables to represent both data and data

relationship among those data.

Each table has multiple column and each column has unique name.

Each table contains records of a particular type.

The Relational Data model is simplified the user’s view of the database.

Tables are related with each other by sharing common entity characteristics

Suppose two tables are CUSTOMER and AGENT.

CUSTOMER table contains fields are CUST_ID , CUST_NAME , CUST_PHONE , AGENT_ID.

AGENT table contains field are AGENT_ID , AGENT_NAME , AGENT_PHONE , AGENT_SAL.

Even data are stored into different table , the common link b/w the CUSTOMER and AGENT table is AGENT_ID.

Although both table are completely independent of one another , data b/w the table can be easily connect using common links.


CUSTOMER

CUST_ID

CUST_NAME

CUST_PHONE

AGENT_ID

AGENT

AGENT_ID

AGENT_NAME

AGENT_PHONE

AGENT_SAL

Advantages of Relational Data Model

1. Simplicity :

Simplicity in Designing.

2. Structural Independence :

Changes in the database structure do not affect the data access.

3. Ease of design , implementation , maintenance and uses :

Relational Data model provides structural and data independence both..

4. Flexible and powerful query capability : SQL

Disadvantages of Relational Model

Hardware Overhead :

It need more powerful computing

hardware and data storage device to

perform RDMS assign tasks.

There fore they tend to be slower than

other database systems.

Meri Dedania

Object Oriented Data ModelsRelational DB is widely successful in variety of

application areas.

However it does not support the distribution of database across the number of servers.

Due to these reasons , ODBMS is developed.

ODBMS is among the most recent approaches to the DBMS.

They started in the engineering and domain application.

And became the favored system for financial , telecommunication , and WWW application and multi media application.

It has capacity of storing different types of

data for example , pictures ,voice , video ,

including text , numbers and so on.

It is capable to combine object oriented

programming with database technology and

thus providing an integrated application

development system.

It provides powerful features like

inheritance , polymorphism.


E-R Data ModelThe E-R model is a high-level data model.

It is based on a perception of a real world that consists of a collection of basic objects.

That object is called entity.

E-R model based on relationship among these objects.

E-R model is widely used in database design.

Some specific Symbols or Blocks are used to represent E-R diagram

Like Rectangular Boxes represent entity.

Oval boxes represent Attributes

Diamond boxes represents relationship.

There is no industry standard notation for Developing E-R Diagram

It Is widely used for designing of relational databases.


Advantages of E-R Model Straight forward relational representation :

Easy Conversion from E-R to other data models

Graphically representation for better understanding.

Disadvantages of E-R model

No industry standard for notation:

Popular for high level design


Semi structured Data Model

The semistructured data model is permits the

specification of data where individual data of same type

may have different set of attributes.

The XML is widely used to represent semistructured

data.


Database Language

A database system provides a database definition

language and database manipulation language to specify

database schema and to express database queries and

update respectively.

These two are not different languages , they are

simply form parts of a single database language , such as

SQL


Data Manipulation Language

A data manipulation language is a language that

enables users to access or manipulate data as organized

by the appropriate data model.

The types of access are :

1) Retrieval of information stored in the database.

2) Insertion of new information into the database

3) Deletion of information from the database

4) Modification of information stored in the database


These are basically two types :

1. Procedure DMLs : require a user to specify whatdata are needed and how to get those data.

2. Non Procedure DMLs : It is called Declarative DMLs also. Require a user to specify what data are needed without specifying how to get those data.

Declarative DMLs are usually easier to learn and use than are procedural DMLs.

However , since a user does not have to specify how to get the data , the database systems has to figure out an efficient means of accessing data.

A query is a statement requesting the retrieval of information.

The portion of a DML that involves information retrieval is called a query language.


Although technically incorrect , it is common practice

to use the terms query language and data manipulation

language synonymously.

There are a number of database query language is use

, either commercially or experimentally.

insert , delete , update


A language by which we can specify database schema

by a set of definitions that is called data definition

languages.

The DDL is also used to specify additional properties

of the data.

We can specify storage structure and access methods

used by the database system by a set of statement in a

special type of DDL called data storage and

definition language.

This statement define the implementation details of

the database schemas, which are usually hidden form

the users.

Data-Definition Language


The data value stored in the database must satisfy

certain consistency constraints.

i.e the balance on an account should not fall below

$100.

The DDL provides facilities to specify such

constraints.

The database system check this constraints every time

and database is update.

Create , alter , drop , truncate, rename


Domain Constraint :

Every attributes has domain with possible values.

Declaring an attribute to be of a particular domain

acts as a constraint on the values that it can take.

Domain constraints are the most elementary form of

integrity constraint.

They are tested easily by the system whenever a new data

item is entered into the database.


Referential IntegrityThese are cases where we wish to ensure that a value

that appears in one relation for a given set of attribute

also appears for a certain set of attributes in another

relation.

Database modification can cause violations of

referential integrity.

When a referential integrity constraints is violated ,

the normal procedure is to reject the action that

caused the violation.

Assertions

An assertion is any condition that the

database must always satisfy.

Domain constraints and referential integrity

constraints are special forms of assertions.

However , there are many constraints that

we cannot express by using only these

forms.

For example , “Every loan has at least one

customer who maintains an account with a

minimum balance of $1000.00” must be

expressed as an assertion.

When an assertion is created , the system

tests it for validity.

If the assertion is valid , then any future

modification to the database is allowed

only if it does not cause that assertion to

be violated.

Authorization We may want to differentiate among the users as

far as the types of access they are permitted on various data values in the database.

These differentiations are expressed in terms of authorization , the most common being ;

read authorization , which allows reading ,but not modification of data.

insert authorization , which allows insertion of new data , but not modification of existing data.

Update authorization , which allows modification but not deletion of data.

Delete authorization , which allows deletion of data.

We may assign the user all , none or a combination of these types of authorization.

The DDL , just like any other programming language , gets an input some instruction and generate some output.

The output of the DDL is the placed in the data dictionary , which contains meta data , that about data about data.

The Data dictionary is considered to be a special types of table , which can only be accessed and updated by database system itself.

The database system consultants the data dictionary before reading or modifying actual data

DCL (Data Control Language)

GRANT - gives user's access privileges to database

REVOKE - withdraw access privileges given with the GRANT command

TCL (transaction control language)

Commit : save work done

Rollback : restore database to original since the last COMMIT

DQL (Data Query Language)

select

Meri Dedania

database management system by - merry patel · database management system by ... data redundancy...

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