Database Management Systems.pptx

8/10/2019 Database Management Systems.pptx

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Database Management Systems

An introduction

January 11, 2015 1EED, NIT Calicut


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Database System

A very large integrated collection of data of

the entities and relationships

Database system tries to model the real world

systems and the underlying hierarchies, data

(information)flows etc.

A Database Management System (DBMS) is a

software package designed to store and

manage databases.

January 11, 2015 EED, NIT Calicut 2


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Why Study Databases?

Many computing applications deal with large

amounts of information

Database systems give a set of tools for storing,

searching and managing this information

Databases are a core topic in computer science

Basic concepts and skills with database systems

will help Engineers to deal with many computerizedinformation systems, CAD tools, GIS, etc



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Informatics

Study of database systems has graduated as a

major field of specialization namely

Informatics

Eg. Bioinformatics



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Data and Database

A database is a collection of related data

By data we mean known facts that can be

recorded and that have implicit meaning

Eg. The name of a person becomes data for

the Institute if he/she is a student or

employee or supplier or examiner or some of

that kind of relation exists



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Database

A database has many implicit properties

1. A database represents some aspects of the

real world sometimes called the mini world

or the Universe of Discourse(UoD)

Changes to the mini world are reflected in

the database



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Properties of database

2. A database is a logically coherent collection of

data with some inherent meaning. A random

assortment of data cannot correctly be

referred to as a database



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3. A database is designed, built and populated

with data for a specific purpose. It has an

intended group of users and some pre

conceived applications in which these users

are interested.



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4. A database can be of any size and of varying

complexity

5. A database may be generated and maintained

manually or it may be computerized

For small scale use, computerization is a waste

but for large scale application computerization

is very complex but highly effective in

management, reporting monitoring etc



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6. A computerized database may be created andmaintained either by a group of applicationprograms written specifically for that task or by adatabase management system

Commercial DBMS

ORACLE

SAP

DBFOXPRO

MS ACCESS



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Database Management System(DBMS)

A database management system(DBMS) is a

collection of programs that enables users to

create and maintain database. A DBMS helps

in

Defining

Constructing

Manipulating

For various applications



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Defining Database

Specifying the data types

Defining structures for the data

Specifying the constraints



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Constructing Database

Building the database on a suitable medium

MS ACESS works on PC environment

SAP works on large systems

ORACLE can be customized to PC or LAN or even

Distributed Systems



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Manipulating Database

Querying the database to retrieve specific

data

Updating the database to reflect changes in

the mini world

Generating reports from the data



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Database System

A database system consists of the DATABASE andthe DBMS Software

MIS- Management Information System

DSS-Decision Support System ERP-Enterprise wide Resource Planning solution

DCS-Distributed Control System

SCADA-Supervisory Control & Data Acquisition system

End to End Solution(Total Solution for all functionalrequirements)

Custom Solution(Partial solution for a particular purpose)



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Characteristics of DBMS

Program-Data independence

The structure of the data files is stored in the

DBMS catalog separately from the access

programs

Program-Operation independence



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Data Modeling

Data modeling is very essential to understand theextent and variety of information that are to be

collected and stored to serve the intended

purpose

The more deeper the understanding of the systemfunctions, interdependence and the end user

requirements or the purposes, the better will be

the data models we develop



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Data Modeling

Data modeling begins with the use of high

level conceptual data models for database

design

Data modeling involves four steps\

Requirement collection and analysis

Conceptual Design

Implementation of database

Physical design phase



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Requirement collection and analysis

- Interview with prospective database users

- Understand and document their datarequirements

- Understand the functional requirements ofthe applications

- Know the user defined

operations(transactions) that will be appliedto the database

- Know the retrievals and updates needed



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Conceptual Design

Create a conceptual schema for the database usinga conceptual high level data model

-it will give a concise description of the datarequirements of the users

-it do not contain the implementation details

-it can be used for communicating with the nontechnical users

-it can also be used to analyze the extent to whichthe users data requirements are met and thatthe conflicts are resolved/avoided



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Implementation of database

3. The next step after data model/design is theactual implementation of the database, usinga commercial DBMS

-for this we need data model mapping(logicaldesign)

-this converts the high level data model to the

implementation data model-Fine-tuning the requirements considering thedata availability, capability of the DBMS etc



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Physical design phase

Internal storage structures

Access modes/paths

File organization for the database files



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Going to the Mini World!!



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Data Modeling using Entity &

Relationship Model

EntityRelationship(ER) Model is a popular

high level conceptual data model

The ER model describes data as entities,

relationships and attributes



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STUDENT

NAME

BRANCH

COURSE

ROLLNOADMYEAR

GRADE

CREDIT


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COURSE

CODE TITLE

CREDIT

SLOTTYPE

DEPT


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FACULTY

EMPCODENAME

DESIG

COURSE

DEPT


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FACULTY STUDENT

COURSE

OFFER

CREDIT

ADVISE


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Entity, Attributes and Data

The ER model describes data as entities,

relationships and attributes

Entities and Attributes

The basic object that the ER model represent is an

entity, which is a thing in the real world with an

independent existence

Physical existence-person, car, grocery item,

Conceptual existence-company, job, university course,



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Entity & Attributes

Each entity has attributes

These are particular properties that describe it

A particular entity will have a value for each of

its attributes(may be at a given instant of

time)

The attribute value that describe each entity

become a major part of the data



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Types of Attributes

Several types of attributes occur to the ER

model

Simple vs composite

Single valued vs multivalued

Stored vs derived



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Composite vs Simple

Eg. Name can be a composite attribute if we

want to separate sirname, first name etc

Composite attributes can be divided into

smaller sub parts which represent more basic

attributes with independent meanings

The value of a composite attribute is the

concatenation of the values of the constituent

simple attributes



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Single vs multivalued

Most attributes have a single value for aparticular entity. Such attributes are calledsingle valued

Employee is an entity

Data of Birth single valued attribute

Qualification multivalued attribute

A multivalued attribute may have a lower andupper bound on the number of values allowedfor each individual entity



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Stored vs Derived

Some attribute like Age can be derived from

another attribute DateofBirth

Some attributes can be derived from related

entities



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NULL Value

A particular entity may not have an applicable

value for an attribute

For such situations, a special value called NULL

is created

Situations

Missing data(data not entered)

Not known values

Not applicable attribute



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Entity type & Entity set

A database usually contains groups of entitiesthat are similar

An entity type defines a collection(or set) of

entities that have the same attribute The collection of all entities of a particular

entity type in the database at any point intime is called an entity set

Entity type and entity set can be given thesame name



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Key Attribute

An important constraint on the entities of an

entity type is the key or uniqueness constraint on

attributes

An entity type usually has an attribute whosevalues are distinct for each individual entity in the

collection

Such an attribute is called a key attribute and itsvalue can be used to identify each entity uniquely

Several attributes could together form key



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Entity & Relationships

Between entities of different type, there exists

relations which makes the data composite and

interdependent for a given database



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Types of Relationships

One to One

One to Many

Many to One

Many to Many



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J 11 2015 EED NIT C li 40

FACULTY STUDENT

COURSE

OFFER

CREDIT

ADVISE

Database Management Systems.pptx

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