Database and RDBMS Concepts Session 1

8/12/2019 Database and RDBMS Concepts Session 1

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Objectives

File Processing System

Data Base Management System

Different types of DBMS


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Data Vs Information

What is data? facts concerning things such as people, objects,

events, etc.

EX : Marks 80 %, 75 %, 65 %, 99%

What is information? data that has been processed and presented in a

form suitable for human interpretation.

Ex : Marks of a Student No. 1998 is 80% inRDBMS course.


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Data Vs Information

To derive information from data weneed to Store and Process.

Need systems support to easily

Store

Retrieve

and Modify data


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Traditional Method of Storage

Files

File Management System (O/S)

Application

ProgramsP1 P2 P3 P4

001 Chandu Enr

002 Steve Pdn

003 Hema Enr


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Files in an Organization

Data File

Master files

Transaction files

Others

Computer program files Backup files

Specialized files: Index files & log files.

Other important files

Object File

Library File Executable File / Load Module

Temporary Files

What is the significance of each type of file ?


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Ways of storing data in Files4176 Aniruddha Sarkar CAPS

4181 Manoj Saha WENA

4183 Moushumi Dharchoudhury CENA

4203 Suryanarayana D.V.S.S. SONA

4204 Vivek Rai CAPS

4176 AniruddhaSarkar CAPS

4181 ManojSaha WENA

4183 MoushumiDharchoudhury CENA

4203 SuryanarayanaD.V.S. SONA

4204 VivekRai CAPS

4176,Aniruddha Sarkar,CAPS,4181,Manoj Saha,WENA,4183,Moushumi

Dharchoudhury,CENA,4203,Suryanarayana D.V.S.,SONA,4204,Vivek Rai,CAPS

Predefined length

Uses space/commas as character

separators


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DATADEPENDENCY

INCONSISTENCY

REDUNDANCY

LOSS OF

FLEXIBILITY

MULTIPLE

FILES

UPDATE

PROBLEM

Problems with File approach


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Introduction To

Data Base ManagementSystem?


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Introduction to DatabaseManagement Systems

The most traditional/common way of managing data is to store them infiles.

File processing system

Files can be

Sequential

Indexed

Relative

In this kind of scenario, the files are managed directly by the operatingsystem services

The primary focus here is to manage the files effectively rather thanthe contents of them

Though this mechanism is very good, it has many draw backs


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What are the problems in FileProcessing

File processing system manages files rather than the data in them.

How does it affect me ?

File Processing System does not provide effective security

Either the entire file is secured or it is not

Some part of the file cannot be secured

record or column level security is not available

Any program which works with files has to know the physical as well asthe logical structure of the file

Any change in either physical or logical structure of the file, makesit necessary for the program to be rewritten

Physical Data Dependence

Logical Data Dependence


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Introduction to DBMS

Data Base Management System

A DBMS is a special set of software which is usedto manage data (information)

Following are some of the important functionsof a DBMS

Data is Accurate (Accuracy)

Data is provided within a timeframe (Timeliness) Only required data is provided (Relevancy)


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The Database

Database is a set of inter-related data

stored centrally on any online mediumwith controlled redundancy which canbe shared by multiple application /

users with a practical ease.


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A database is a repository of integrated &

shared data

The Database

Computer based record-keeping system

Collection of interrelated (persistent)

dataRecords & maintains data

Represents real world objects


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DBMS and File ProcessingSystem

A database is a collection of data

All the information is available centrally

A file is a collection of bits and piecesstored together as a single entity.

A database system internally relies on the

file processing system to manage its data Externally to the user, he feels that he is

storing data, rather than a file


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Advantages of Database

Redundancy can be reduced

Inconsistency can be avoided

Sharing of DataStandards can be enforced

Security restrictions can be applied

Integrity of data can be maintainedConflicting requirements can be balanced


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Database ManagementSystem

Interface between user & DB

Constructs, expands & maintains the DB

File creation / deletion

Adding, deleting & modifying records

Selecting records (queries)

Manages one or more databasesHigher level of abstraction


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Application Programs usingDBMS Services

Application

Programs

DBMS

File System

Storage

A1 A2 A3


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App. pgmmer

Interface thro High

level language

OS (File Mgr, Disk Mgr)

End userApp. pgmmer

Interface thruQuery

OS (File Mgr, Disk Mgr)

DBMS

Where does DBMS fit ?

End user End user

Physical Storage

(Hardware)

Physical Storage

(Hardware)


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DBMS Architecture

Conceptual level

Internal level

External

View

External

View

External

View

DBMS interface

DBMS interface

DISK(s)


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Emp. Name

Emp. Address

Emp. NameEmp. SSNEmp. AddressEmp. Annual_Salary

Emp. Name : string(25)Emp. SSN : Integer, Primary key

Emp. Address : string(50)Emp. Skill : String(6)Emp. Annual_Salary : Dec(9,2)

Name : string, length 25, offset 0SSN : Integer, length 4, offset 25,

INDX unique indexAddress : string, length 50, offset 29Skill : String, length 6, offset 79Annual_Salary : dec (9,2),length 5, offset 85

External

view

Conceptual view

Internal view

User1

User2

DBA


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Interaction with DBMS

A user issues an access request using someparticular sub-language (typically SQL)

The DBMS intercepts the request & interpretsit

The DBMS inspects, in turn, the externalschema, the external/conceptual mapping,the conceptual schema, theconceptual/internal mapping & storagestructure definition

The DBMS performs the necessary operationson the stored DB


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Data sub-languageGenerally data sub-language (DSL) is embeddedin a host language like C or COBOL

Data Definition Language (DDL) :defines & describes the DB objects

Data Manipulation Language (DML) :

supports the manipulation or processingsuch objects


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Users of a DBMS

Database Administrator(DBA)

Database Designer

Application Programmer & SystemAnalyst

End users


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Characteristics of DBMS

Data independence

Speedy handling of spontaneous

information requestsNon-Redundancy

Versatility in representing relationships

between data itemsSecurity protection

Real Time accessibility

f d ff


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Comparison of differentsystems

For better understanding we have broken the different types of data processingsystems into the following four categories

Rudimentary I/O software

Programs working with flat files

COBOL or C language

File Storage with Access Method

Programs working with file managers like VSAM or ISAM or Btrieve

COBOL or C Language

Database Management System

Programs written in COBOL or C or Java to work with RDBMS like DB2,Oracle or Sybase

Programs written in COBOL or RPG to work with Hierarchical andNetwork DBMS

Lot of efforts in generating reports

Advanced Management Tools

Use of Rapid Application Development Tools like Report Generator orForms Generator for creating large applications

C i f iff


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Comparison of DifferentSystems

Rudimentary I/OSoftware

File Storage with Accessmethod

Database Management Advanced ManagementSystems

No independence Storage Independence Physical DataIndependence

Logical Data Independence

Applicationprogrammer designsthe physical data

layout and embeds itinto his program

Storage units can bechanged withoutchanging program

Physical data structurecan be changed withoutchanging programs

Global logical data bechanged without changingthe program

Applicationprogrammers view ofthe file is same as thephysical structure

Applicationprogrammers view ofthe file is converted intophysical file by thesoftware

Physical databasestructures are completelyseparated from thelogical structures

Schema, subschema andphysical data is absolutelyseparate

Programmer usessimple files

Application programmermore concerned withstructures andaddressing

Application programmermore concerned withstructures andaddressing

Application programs arecompletely insulated fromthe data structures


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Comparison of Different SystemsRudimentary I/O

Software

File Storage with

Access method

Database

Management

Advanced

ManagementSystems

Entirelysequential files

Sequential fileswith some directaccess

Direct access filesfor someapplications

Direct access to alllive data

Data accessed

with primary key

Data accessed

with primary aswell as secondarykeys

Generalized

searching facility

Generalized

searching facility

No attention todata security

Securityproceduresapplied to

individual datafiles

Securityprocedures appliedto individual data

files

Corporate worldwide security

No teleprocessing

Simple remoteinquiry

Remote data entryand inquiry

Complete interactiveprocessing remotely.Computer networksand distributeddatabases


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Different types of DBMS


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Hierarchical ModelP1 Nut Red 12 London

S1 Jones 10 Paris 300

S2 Smith 20 London 300

P2 Bolt Green 17 Paris


S2 Smith 20 London 400

S3 Blake 10 Paris 200

P3 Screw Blue 12 London


P4 Screw Green 17 Paris


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Hierarchical Model

In a hierarchical model a tree likestructure is maintained

For each parent record, there can bemany siblings

The record at the top is called the root

The root may have any number ofdependants. Each of which may havelower level dependants.

D b k f Hi hi l


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Drawbacks of Hierarchicalmodel

Insert It is not possible to insert a supplier who is not

supplying a part currently

Delete Deleting part information will also delete

information about all the suppliers below it

Update If you need to update any supplier information,

you need to search the entire database for thesame supplier and update all the records for thesame supplier.


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Network Model

S1 Smith 20 London S2 Jones 10 Paris S3 Blake 10 Paris

P1 Nut Red 12 London P2 Bolt Green 17 Paris P3 Screw Red 12 Rome P4 Screw Green 10 Paris

300200 500 100

300


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Network Model

In case of network model, data isrepresented by records and links

Many to Many relation can be expressedeasily in a network model

This is not possible in hierarchical model

Records are linked to each other usingconnectors


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Advantages of Network model

Insert You can simply insert a new part or supplier

without any need to establish any link

Delete Deleting a supplier or a part does not delete

recursively

Similarly, just by deleting the connector, the link

between supplier and parts can be broken.Update Since suppliers and parts occur only once,

updating requires only change to be made to asingle record rather than searching and updatingmany records


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Relational ModelS# SNAME STATUS CITY

S1 Smith 20 London

S2 Jones 10 Paris .

S3 Blake 30 Paris .

S

P# Pname Color Weight City .

P1 Nut Red 12 London .

P2 Screw Red 17 Paris .

P3 Bolt Blue 17 Rome .

P4 Screw Yellow 14 London .

P

S# P# Qty

S1 P1 200

S1 P2 100

S1 P3 300

S1 P4 230

S2 P2 100

SP


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Relational Model

In relational model the data is simplyrepresented in the form of tables

If you compare, these three tables closely

resemble sequential filesCompared to the other two models, relationalis simple to understand

There are no links or pointers which connectdifferent tables

The model is called relational because it usesrelational algebra to represent and manage

information


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More On Relational Model

Each row is called as a tuple

Each column is called as a attribute

Domain It is a set of permissible values that can be stored

in an attribute

This feature is not available in the other models

Relational model provides a set of operatorsto the user. Using these operators, the usercan perform any operations on the tables.

Advantages of Relational


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Advantages of RelationalModel

Insert Adding a new supplier or a part is not a problem.

They are independent entities

If you want to represent a relation betweensupplier and parts, then insert a tuple in SP table.

Delete Delete operations are independent of other tables

Update Updating supplier or part information is very

simple

Management Systems


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Management Systems(RDBMS)

The basic functionality of RDBMS wasconceptualized by Dr. E F Codd, when he wasworking for IBM

He laid down certain principles which govern thefunctioning of any RDBMS

In 1974, the first standard of SQL was also

developedAlso C J Date from IBM also contributedtowards standardization of RDBMS


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Commercial Packages

Hierarchical Model : IMS

Network Model : IDMS

Relational Model : DB2, ORACLE,

SYBASE,ACCESS,INFORMIX, SQL Server


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End of Session 1

Database and RDBMS Concepts Session 1

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