part1 background chapter 01- introduction to database system lu wei college of software and...
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Part1 BackgroundChapter 01- Introduction to Database System
Lu Wei
College of Software and Microelectronics
Northwestern Polytechnical University
Database Systems
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Outline
• Introduction• Origin and development of database• Key concepts in database systems• Components of the DBMS environment• Characteristics of database approach• Advantages and disadvantages of DBMS
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Outline
• Functions of DBMS• Components of DBMS• Client-Server Architecture of DBMS • Examples of database systems• Research fields in database technology
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Introduction
• Impact on economic development– The history of database system research is one of
exceptional productivity and startling economic impact.
– Achievements in database research underpin fundamental advances in communications systems, transportation and logistics, financial management, knowledge-based systems, accessibility to scientific literature, and a host of other civilian and defense applications.
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Introduction
– They also serve as the foundation for considerable progress in the basic science fields ranging from computing to biology.
(Silberschatz et al., 1990,1996)
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Introduction
• Application and development of database technology– C
hina Information Technology Application Blue Paper(2007-2008) - Chapter 8
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Introduction
• Database applications in day-to-day life– Purchases from the supermarket– Using the local library– Reserving tickets on line– Using the Internet– …
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Origin and development of database
• Database approach is now the most effective approach for data management. It is necessary for us to review it’s predecessors although these approaches are largely obsolete.
• The approach for data management has gone through three stages – manual management, file-based system, database system.
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Origin and development of database
• Manual management– Used before 1950s– Application background: science computation– Hardware condition: punch tape, punch card,
magnetic tape, no disk– Software condition: no OS, no software for data
management, batch mode for data process– Limitations: data and program are dependent, data
are managed by each application, no need to save data long time, no shared data
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Origin and development of database
Data 1
Data 2
Data n
Program 1
Program 2
Program n
Figure 1-1 phase of manual management
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Origin and development of database
• File-based System– A collection of application programs that perform
services for the end-users such as the production of reports. Each program defines and manages its own data.
– Used between 1950s and 1960s– Application background: science computation, data
management– Hardware condition: disk, drum
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Origin and development of database
– Software condition: have special data management software - file systems in OS, real time process data online (besides batch)
– Limitations: data are separate and isolated, uncontrolled duplication of data, data and program are dependent, incompatible file formats
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Origin and development of database
File1
File2
Filen
Prog1
Prog2
Progn
File System
Figure 1-2 phase of file system
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Origin and development of database
• Database system– Used since 1960s– Application background: large scale data
management– Hardware condition: disk with large capacity, the price
of hardware falls down– Software condition: a unified special data
management software – database management system appeared
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Origin and development of database
Database
Prog1
Prog2
Progn
DBMS
Figure 1-3 phase of database system
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Key concepts in database systems
• Data – Data are raw facts that describe people, objects, and
events.
• Information – Information are images that denote the status of
objects and its’ evolvement.
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Key concepts in database systems
• Database – A shared collection of logically related data, and a
description of this data, designed to meet the information needs of an organization.
– Related – Integrated or shared– Structured – Keep data long time– Large quantities of data
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Key concepts in database systems
• Database Management System (DBMS)– A software system that enables users to define, creat
e, maintain, and control access to the database.– DBMS is the interface between the user’s application
programs and the database– Oracle, DB2, SQLServer, MySQL, Sybase, PostgreS
QL,…
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Key concepts in database systems
• History of Database Management Systems– DBMS has its roots in the 1960s Appllo moon-landing
project.– NAA(美国北美航空公司 ), the prime contractor for the
project, developed software known as GUAM (Generalized Update Access Method). It is a hierarchical structure.
– 1960s, IBM joined NAA to develop GUAM into IMS (Information Management System)
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Key concepts in database systems
– Mid-1960s,IDS (Integrated Data Store) emerge from General Electric. It is a network DBMS.
– 1970, E.F,Codd of IBM Research Laboratory produced his high influential paper on the relational data model.
– System R project at IBM San Jose Research Laboratory in California
• structured query language (SQL) become standard language for relational DBMSs;
• DB2, SQL/DS, Oracle, …
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Key concepts in database systems
• Database system– A database system is developed to support the operat
ions of a specific organization or a specific set of applications.
– A Database System consists of :• an application specific database • the DBMS that maintains that database • the application software that manipulates the database
– Figure 1-4 illustrates a simplified database-system architecture.
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Key concepts in database systems
Figure 1-4 database-system architecture
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Components of the DBMS environment
• Hardware – The DBMS and the applications require hardware to
run. The hardware can range from a single personal computer, to a single mainframe, to a network of computers.
– Disk space– Main memory– …
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Components of the DBMS environment
• Software – DBMS– Operating system– Application programs– High language which interface with the database and
it’s complier system– Network software (sometimes)
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Components of the DBMS environment
• Roles– Data and Database Administrators (DA and DBA)– Database Designers
• Logical Database Designers• Physical Database Designers
– Application Developers– End-Users
• Naïve users• Sophisticated users
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Characteristics of database approach
• Data Abstraction– DBMSs allow data to be structured in ways that make
it more understandable and meaningful to the applications than the ways data are physically stored on disks.
– The DBMS stores the structure of the data as part of the description of the database in the system catalog, separately from the application programs.
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Characteristics of database approach
• Reliability– DBMSs provide high reliability by
1) enforcing integrity constraints• Integrity constraints reflect the meaning (or, the semantics)
of the data and of the application. • Data type of each data item - An alphanumeric character str
ing of maximum length 10
2) ensuring data consistency • When the system fails, DBMSs guarantee data consistency;
that is, interrupted update operations do not corrupt the database with values that violate the integrity constraints and no data in the database is lost.
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Characteristics of database approach
• Efficiency – DBMSs support both efficient space utilization and effi
cient access to data. – By making use of the data description in the catalog,
DBMSs are able to minimize data redundancy, which in turn saves both space and processing time.
– DBMSs enhance the performance of queries by means of optimizations and the use of access methods to data based on their values.
– DBMSs decrease response time of transactions by allowing multiple users to access the database concurrently.
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Advantages and disadvantages of DBMS
• Advantages of DBMS– Control of data redundancy– Data consistency– More information from the same amount of data– Sharing of data– Improved data integrity– Improved security– …
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Advantages and disadvantages of DBMS
• When Is a Database Management System Needed? – Large quantities of related data need to be stored– Require efficient data sharing among many users – Security and access control is crucial– Require a real quality of service to be a part – …
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Advantages and disadvantages of DBMS
• Disadvantages of DBMS– Complexity– Size– Cost of DBMSs– Additional hardware costs– Cost of conversion– Performance– High impact of failure
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Advantages and disadvantages of DBMS
• All the services and guarantees that a database management system offers us incur some overhead cost—nothing is free. – DBMS need to be buy– DBMS require some minimum hardware configuration– Learning to use and maintain a DBMS
• Whether a database management system is a good environment worth purchasing for a given application depends on the functional requirements of the application.
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Advantages and disadvantages of DBMS
• When Is a Database Management System Not Needed? – The data has a simple structure and its size is small. – The application, although simple and unchanging, has
a special purpose. – Concurrent access to data by multiple users is not req
uired.
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Functions of DBMS
• Data storage, retrieval, and update• A user-accessible catalog• Transaction support• Concurrency control services• Recovery services• Authorization services• Support for data communication• Integrity services• Services to promote data independence• Utility services
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Components of DBMS
Application programs
Queries Database schema
DML preprocessor
Query processor
DDL compiler
Program object code
Database manager
Dictionary manager
File manager
Access methods
System buffers
Database and
system catalog
DBMS
Figure 1.5 Major components of a DBMS
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Components of DBMSProgram
object codeQuery
processorCatalogmanger
Authorizationcontrol
Commandprocessor
Integritychecker
Queryoptimizer
Transactionmanager Scheduler
Buffermanager
Recoverymanager
Filemanager
Accessmethods
Systembuffers
Database and system catalog
Data manager
Figure 1.6 Components of a database manager
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Client-Server Architecture of DBMS
• We will discuss the architecture of DBMS in detail in chapter 12
Figure 1.7 Client-server architecture
LAN
Client1
Client2
Client3
Server(with DBMS)Database
Requests for data Selected data returned
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Examples of database systems
• A Library Database System• An E-Store Database System
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Research fields in database technology
• Research and develop or improve the DBMS and related middleware
• Database design– methodology– tools– theory– Standard and criterion
• Theory of database– Normalization– Knowledge Discovery from Database (KDD), …
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Summary
• In this chapter you should have learned:– The development of the approach for data
management and it’s three stages– The concepts of database, DBMS, Database System– Characteristics of database approach– Advantages and disadvantages of DBMS– The main components and functions of DBMS