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DBMS

Introduction to Database Management System

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DBMS

Data vs. Information

Data

Raw facts, text, graphics, images, sound and video segments that

have meaning in the user’s environment

Information

Data that have been processed in such a way as to increase the

knowledge of the person who uses the data

Data are raw facts. Information is processed data to

reveal the meaning behind the facts.

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DBMS

Traditional Approach

Systems used files to store information

Separate systems - Separate files and programs for each application

E.g. Payroll files, Personnel files, Accounts files etc.

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DBMS

Example of file system

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DBMSSome Problems with Traditional File

Processing Systems

Redundancy (duplication of data)

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DBMSSome Problems with Traditional File

Processing Systems

Redundancy (duplication of data)

wasteful of space (storage)

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DBMSSome Problems with Traditional File

Processing Systems

Redundancy (duplication of data)

wasteful of space (storage)

update inefficiencies

Module Title?

DBMSSome Problems with Traditional File

Processing Systems

Redundancy (duplication of data)

wasteful of space (storage)

update inefficiencies

(when a teacher moves to a new address,

or changes her name, the teacher's

"record" must be changed each place it is

stored)

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DBMSSome Problems with Traditional File Processing

Systems

Redundancy (duplication of data)

wasteful of space (storage)

update inefficiencies

(when a teacher moves to a new address,

or changes her name, the teacher's

"record" must be changed each place it is

stored)

data inconsistency (different addresses for

the same teacher in different files)

Module Title?

DBMSSome Problems with Traditional File Processing

Systems

Redundancy (duplication of data)

wasteful of space (storage)

update inefficiencies

(when a teacher moves to a new address, or

changes her name, the teacher's "record" must

be changed each place it is stored)

data inconsistency (different addresses for the same

teacher in different files)

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DBMS

LIMITATIONS OF FILE-BASED

SEPARATION AND ISOLATION

Payroll Office files has the teachers' names and id's and departments

Principal's Office Files has teacher’s names , the current salary scale

and date this salary scale became effective

Asst. Principal's Office files has seminar topics for each teacher

PROGRAM & DATA DEPENDENCE

The Payroll Department has written some lengthy Pascal programs to

access their files and perform queries and reports.

The Personnel Department has written some C programs to access

their files and perform queries and reports.

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DBMS

Database Approach

Build a SINGLE pool of interrelated files, rather than

SEPARATE collection of files.

(This is an INFORMAL description of a database).

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DBMS

DATABASE

A COLLECTION OF SELF-DESCRIBING AND

INTEGRATED ,ORGANISED DATA

(Kroenke's Definition of a Database)

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DBMS

DATABASE MANAGEMENT SYSTEM (DBMS)

A collection of Programs that enables you to Store, modify, and

extract (access) information from a database.

Provides the interface between the user and the data in the

database

Allocates storage to data and maintains indices so that any

required data can be retrieved.

Protects data against corruption

Provides recovery and restart facilities after a hardware or

software failure.

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DBMS

Database System:

The DBMS software together with the data itself. Sometimes,

the applications are also included.

ApplicationApplicationApplicationApplicationDBMSDBMSDBMSDBMS data

catalog

database

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DBMS

Database vs. File Systems

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DBMS

DATABASE MANAGEMENT SYSTEM (DBMS)

The following are examples of Database Applications:

Banking: all transactions

Airlines: reservations, schedules

Universities: registration, grades

Sales: customers, products, purchases

Manufacturing: production, inventory, orders, supply chain

Human resources: employee records, salaries, tax deductions

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DBMS

Different DBMS Software

• ORACLE• ACCESS• SQL SERVER• IBM DB2• Sybase• SAP DB• PostgreSQL• MySQL• MS SQL Server, ...

DATABASE MANAGEMENT SYSTEM (DBMS)

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DBMS

Advantages of Database Approach

Controlling redundancy in data storage and in development and

maintenance efforts.

Sharing of data among multiple users.

Restricting unauthorized access to data.

Greater consistency of data

Enforcing integrity constraints on the database.

Providing backup and recovery services.

Availability of up-to-date information.

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DBMS

Database System EnvironmentDatabase System Environment

Application Programs/ Queries

DBMS Software

Software to ProcessQueries/ Program

Software to AccessStored Data

Stored Database

Stored DataDefinition

(Meta-Data)

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DBMS

Data Models

Data Model is a set of concepts that can be used to describe

the structure of a database

data types, relationships, and constraints

Data Model Examples:

Relational - describes database structure as tables

Network - describes database structure as a network

Object Oriented - describes database structure as objects

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DBMS

HISTORY OF DATABASE SYSTEMS

• FIRST GENERATION

_ HIERARCHICAL MODEL

• INFORMATION MANAGEMENT SYSTEM (IMS)

– NETWORK MODEL

• CONFERENCE ON DATA SYSTEM LANGUAGES (CODASYL)

• DATA BASE TASK GROUP (DBTG)

• SECOND GENERATION

– RELATIONAL MODEL

• E. F. CODD

• DB2, ORACLE

• THIRD GENERATION

– EXTENDED RELATIONAL DATA MODEL OR OBJECT-RELATIONAL DATA MODEL

– OBJECTED-ORIENTED DATA MODEL

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Schema Architecture

Database Schema: The description of a database. It Includes

descriptions of the database structure and the constraints

that should hold on the database.

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DBMS

The three-schema architecture.

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DBMS

The three-schema architecture.

External schema describes part of a database that a particular

user or users are interested in.

Using the relational model, these are views

Conceptual schema describes the structure of he whole

database for a community of users.

Using the relational model, these are tables

Internal schema describes the physical storage structure of the

database.

These are not tables, this is the data as stored by the DBMS.

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DBMS

ROLES IN DATABASE ENVIRONMENT (USERS)

DATA ADMINISTRATOR Implements the database

APPLICATION PROGRAMMER Interact with the database through high level programming

END-USER Interacts and uses the database

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DBMS

Data Dictionary

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DBMS

Database Languages

Data Definition Language (DDL)

Used to define the conceptual and internal schemas

Data Manipulation Language (DML)

Used to describe operations on the instances of a database

Procedural DML (how) vs. declarative DML (what)

e.g., Relational Algebra e.g., SQL

Note, SQL includes a DML and a DDL in one!

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DBMS

Database Languages

DCL Data Control Language. [Grant, Revoke commands

(oracle)]

TCL [Transaction control Language] [Commit, Rollback,

savepoint commands (oracle)]

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DBMS

Classification of DBMS based on the data model used:

Relational DBMS

Network DBMS

Hierarchical DBMS

Object-oriented DBMS

Object-relational DBMS

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DBMS

Classification of DBMS based on the number of users:

Single-user (typically used with micro- computers)

Multi-user (most DBMSs).

Classification of DBMS based on the number of sites:

Centralized (uses a single computer with one database)

Distributed (uses multiple computers, multiple databases)