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11 File Systems and Databases
Chapter 1 The Worlds of Database Systems
Prof. Sin-Min Lee
Dept. of Computer Science
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Tuesday Thursday
10:15 – 11:30
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??!
Your evaluation in this course is determined by:
30%
Class Presentation 10%
Presentation report 5%
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11Text Book
NARAYAN S. UMANATH & RICHARD W. SCAMELL, DATA MODELING AND DATABASE DESIGN, 2007 Thomson
11A. Silberschatz, H.F. Korth, S. Sudarshan: Database System
Concepts, 5th Ed., McGraw-Hill, 2006. A. Silberschatz, H.F. Korth, S. Sudarshan: Database System
Concepts, 5th Ed., McGraw-Hill, 2006.
GOOD REFERENCE
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The mediocre teacher tells.
The good teacher explains.
The superior teacher demonstrates.
The great teacher inspires.
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Files and DatabasesFiles and Databases
File: A collection of records or documents dealing with one organization, person, area or subject (Rowley) Manual (paper) files Computer files
Database: A collection of similar records with relationships between the records (Rowley) Bibliographic, statistical, business data, images, etc.
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Introducing the DatabaseIntroducing the Database
Major Database Concepts Data and information
Data - Raw facts
Information - Processed data
Data management
Database
Metadata
Database management system (DBMS)
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Figure 1.1
Sales per Employee for Each of ROBCOR’S Two Divisions
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Database SystemsDatabase Systems Types of Database Systems
Number of Users Single-user
– Desktop database Multiuser
– Workgroup database– Enterprise database
Scope Desktop Workgroup Enterprise
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Database SystemsDatabase Systems
Types of Database Systems Location
Centralized Distributed
Use Transactional (Production) Decision support Data warehouse
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DatabaseDatabase
A Database is a collection of stored operational data used by the application systems of some particular enterprise (C.J. Date) Paper “Databases”
Still contain a large portion of the world’s knowledge File-Based Data Processing Systems
Early batch processing of (primarily) business data Database Management Systems (DBMS)
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Why DBMS?Why DBMS?
History 50’s and 60’s all applications were custom built for particular
needs File based Many similar/duplicative applications dealing with collections
of business data Early DBMS were extensions of programming languages 1970 - E.F. Codd and the Relational Model 1979 - Ashton-Tate and first Microcomputer DBMS
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File Based SystemsFile Based Systems
Naughty
NiceJust what asked for
CoalEstimation
DeliveryList
Application File
ToysAddresses
Toys
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From File Systems to DBMSFrom File Systems to DBMS
Problems with file processing systems Inconsistent data Inflexibility Limited data sharing Poor enforcement of standards Excessive program maintenance
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DBMS BenefitsDBMS Benefits
Minimal data redundancy Consistency of data Integration of data Sharing of data Ease of application development Uniform security, privacy, and integrity controls Data accessibility and responsiveness Data independence Reduced program maintenance
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Terms and ConceptsTerms and Concepts
Data independence Physical representation and location of data and the use of
that data are separated The application doesn’t need to know how or where the
database has stored the data, but just how to ask for it Moving a database from one DBMS to another should not have
a material effect on application program Recoding, adding fields, etc. in the database should not affect
applications
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Database EnvironmentDatabase Environment
CASE Tools
DBMS
UserInterface
ApplicationPrograms
Repository Database
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Database ComponentsDatabase ComponentsDBMS
===============
Design toolsTable CreationForm CreationQuery CreationReport Creation
Procedural language
compiler (4GL)=============
Run timeForm processorQuery processor
Report WriterLanguage Run time
UserInterface
Applications
ApplicationProgramsDatabase
Database contains:User’s DataMetadataIndexesApplication Metadata
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Types of Database SystemsTypes of Database Systems
PC databases Centralized database Client/server databases Distributed databases Database models
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PC DatabasesPC Databases
E.g.:AccessFoxProDbaseEtc.
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Centralized DatabasesCentralized Databases
Central Computer
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Client Server DatabasesClient Server Databases
NetworkClient
Client
Client
DatabaseServer
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Distributed DatabasesDistributed Databases
computercomputer
computer
Location A
Location CLocation B
HomogeneousDatabases
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Distributed DatabasesDistributed Databases
Local Network
DatabaseServer
Client
Client
CommServer
Remote Comp.
Remote Comp.
HeterogeneousOr FederatedDatabases
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Introducing the DatabaseIntroducing the Database Importance of DBMS
It helps make data management more efficient and effective.
Its query language allows quick answers to ad hoc queries.
It provides end users better access to more and better-managed data.
It promotes an integrated view of organization’s operations -- “big picture.”
It reduces the probability of inconsistent data.
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Figure 1.2
The DBMS Manages the Interaction
Between the End User and the Database
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Introducing the DatabaseIntroducing the Database
Why Database Design Is Important?
A well-designed database facilitates data management and becomes a valuable information generator.
A poorly designed database is a breeding ground for uncontrolled data redundancies.
A poorly designed database generates errors that lead to bad decisions.
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Historical RootsHistorical Roots Why Study File Systems?
It provides historical perspective.
It teaches lessons to avoid pitfalls of data management.
Its simple characteristics facilitate understanding of the design complexity of a database.
It provides useful knowledge for converting a file system to a database system.
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Figure 1.3
Contents of the CUSTOMER File
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Table 1.1 Basic File TerminologyData “Raw” facts that have little meaning unless they have been
organized in some logical manner. The smallest piece of datathat can be “recognized” by the computer is a singlecharacter, such as the letter A, the number 5, or somesymbol such as; ‘ ? > * +. A single character requires onebyte of computer storage.
Field A character or group of characters (alphabetic or numeric)that has a specific meaning. A field might define a telephonenumbers, a birth date, a customer name, a year-to-date(YTD) sales value, and so on.
Record A logically connected set of one or more fields that describesa person, place, or thing. For example, the fields thatcomprise a record for a customer named J. D. Rudd mightconsist of J. D. Rudd’s name, address, phone number, dateof birth, credit limit, unpaid balance, and so on.
File A collection of related records. For example, a file mightcontain data about ROBCOR Company’s vendors; or, a filemight contain the records for the students currently enrolledat Gigantic University.
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Figure 1.4
Contents of the AGENT File
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A Simple File System
Figure 1.5
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