Download Introduction to Database System

DBMS
Introduction to Database Management System
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Data vs. Information
DBMS
 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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Traditional Approach
DBMS
 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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Example of file system
DBMS
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Some Problems with Traditional File Processing
DBMS
Systems
Redundancy (duplication of data)
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Some Problems with Traditional File Processing
DBMS
Systems
Redundancy (duplication of data)
wasteful of space (storage)
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Some Problems with Traditional File Processing
DBMS
Systems
Redundancy (duplication of data)
wasteful of space (storage)
update inefficiencies
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Some Problems with Traditional File Processing
DBMS
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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Some Problems with Traditional File Processing
DBMS
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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Some Problems with Traditional File Processing
DBMS
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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LIMITATIONS OF FILE-BASED
 SEPARATION AND ISOLATION
DBMS
 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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Database Approach
DBMS
 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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DATABASE
DBMS
 A COLLECTION OF SELF-DESCRIBING AND INTEGRATED
,ORGANISED DATA
(Kroenke's Definition of a Database)
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DATABASE MANAGEMENT SYSTEM (DBMS)
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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Database System:
DBMS
 The DBMS software together with the data itself. Sometimes,
the applications are also included.
database
Application
DBMS
data
catalog
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Database vs. File Systems
DBMS
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DATABASE MANAGEMENT SYSTEM (DBMS)
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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DATABASE MANAGEMENT SYSTEM (DBMS)
DBMS
Different DBMS Software
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ORACLE
ACCESS
SQL SERVER
IBM DB2
Sybase
SAP DB
PostgreSQL
MySQL
MS SQL Server, ...
Advantages of Database Approach
DBMS

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
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Enforcing integrity constraints on the database.
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Providing backup and recovery services.
 Availability of up-to-date information.
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Database System Environment
DBMS
Application Programs/ Queries
DBMS
Software
Software to Process
Queries/ Program
Software to Access
Stored Data
Stored Data
Definition
(Meta-Data)
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Stored
Database
Data Models
DBMS
 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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HISTORY OF DATABASE SYSTEMS
DBMS
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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
Schema Architecture
DBMS
 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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The three-schema architecture.
DBMS
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The three-schema architecture.
DBMS
 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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ROLES IN DATABASE ENVIRONMENT (USERS)
DBMS
 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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Data Dictionary
DBMS
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Database Languages
DBMS

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
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e.g., SQL
Note, SQL includes a DML and a DDL in one!
Database Languages
DBMS
 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)
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