Unit I Definitions

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UNIT I

INTRODUCTION

Tuesday, May 10, 2011 1www.gsb.co.in


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Database Systemsy A database system is a term that is typically used to

encapsulate the constructs of a data model, database

Management system (DBMS) and database.

y Adatabase system is a computer based record keepingSystem whose overall purpose is to record and

maintain information that is relevant to theorganization necessary for making decisions.



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Databasey Database is an organized collection of logically related

data.

y A

database may be of any size and complexity.

y Example:y Sales person my maintain small database consisting of

few megabyte.

y Alarge corporate may build a large database consistingof several terabyte.

y Avery large company build a very large databaseconsisting of several tetrabyte.



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Datay Stored representations of objects and events that

having meaning and importance in the users

environment.y Example: Sales persons database contains

y Customers name, Address, Contact Number, Sold Item , whatprice. (Structured Data)

y Data types are: Numeric, Character, and dates.

y These are in Tabular Form.(Tables, relations, Spread sheetetc)



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y Example:

y Database are used to stored Objects such as documents,Maps, Images etc. (Unstructured Data or multimedia data).

y Sales persons database may contain images of the customers.

y Multimedia datas are most often found on Web enableddatabase.

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Informationy The term data and information is closely related.

y Information as a data that have been processed in such

a way as to increase the knowledge of the person whouses the data.

y Example

y Ram, Kannan A 2011052521

y

Raj, Kumar K 2011059859y Mary, Helen I 2011057851

y The data remain useless bcs., we have no idea what itmean.



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y By adding a few additional data items


Name ID Major CGPA

Ram, Kannan A 2011052521 Finance 9.52Raj, Kumar K 2011059852 Operation 7.85

Mary, Helen I 2011057851 HR 8.32


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Metadatay data about data

y Data that describe the properties or characteristic of

end user data.y Metadata describe the properties of data but are

separate from data.

yWith clear meaning data can be confusing,

misinterpreted, or erroneous.y Metadata are stored as a part of the database.



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Name Type Length Min Max Description

Source

Course Alphanumeric

30 Course IdandName

AcademicBlock

Section Integer 1 1 9 SectionNumber

Register

SemesterA

lphanumeric 10 Semesterand year Register

Name Alphanumeric

30 StudentName

StudentIS

ID Integer 9 StudentID

StudentIS


Data Item Metadata


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Database Management Systemy ASoftware system that is used to create, maintain, and

provide controlled access to user database.

yProvides a systematic method of creating, updating,sorting and retrieving data in database.

y Enables end user and application programmers toshare data.

y Enables data to be share among multiple application,rather than store new files for every applications.

y Controlling data access, enforcing data integrity,managing concurrency control and restoring database



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Data Modelsy Graphical system used to capture the nature and

relationship among data.

y Levelsy Enterprise Data Models

y Less detailed and captures the major categories of data and therelationship between data.

y Comprehensive to the whole organization.

y Explain scope of data covered in the database.

y Projected-level Data Modelsy More detailed and more closely match the way the data must be

include in the database.

y Used in the process of a developing a database and applicationsagainst it.



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Data Models


Customer

Order

Product

Places

Is Placed by

contains

Is contained in

CustomerID/ Name

ProductID/ Price

OrderID/ C_ID/ Order Date

Order LineQty

Places

Is Placed by

contains

Has

Is contained in

Is for

1:M

M:N


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Entitiesy An Entity is like a noun in that it describes a person,

place, object, event, or concept in the business

environment for which the information must berecorded and retained.

y Customer and order are the entities.



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Relationshipy Awell structured database establishes many

relationship between entities.

y

Most relationships arey one tor many (1:M)

y Many to many (M:N)

y Relationship is marked by crows foot attached to theEntity (rectangle).

y Enterprise level which include only the higher levelrelationship of customers.

y Project level additional details are there.



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Relational Databasey Adatabase that represents data as a collection of tables

in which all data relationships are represented by

common values in related tables.


Unit I Definitions

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