數(shù)據(jù)庫(kù)原理英文課件chaper1the-world-of-database-systems

1、Database Principles2TextbooksRequired:A First Course in Database Systems, by Jeffrey D.Ullman Jennifer Widom. Recommended: 薩師煊, 王珊. 數(shù)據(jù)庫(kù)系統(tǒng)概論(第三版). 高等教育出版社, 2000 年Books on SQL Server 2000You may also want:Books on design and programming : Powerbuilder, PowerDesigner, UML, VB, Delphi, VC, JAVA, C#, ASP

2、, PHP, JSP etc.3Why Using English Textbook ?More computer English wordsMore advanced and newest informationBetter information retrieval capabilityMore international communication chance4What to learn in this unit ?Basic theories (basic)System and database design (designer)Application Programming (pr

3、ogrammer)Database management and maintenance (database manager)5SyllabusBackground and history of database management systemsFundamentals of using a database management systems: SQL 2000.(*extracurricular)Database modelingRelational model: theoretical background and operations Database Language SQLF

4、undamentals of database management systems: transactions and security etc. Database system design and practiceChapter 1The Worlds of Database SystemsEvolution of Database SystemsArchitecture of DBMS and DBSFuture of Database Systems71.1 Evolution of Database Systems1.1.1 Some Basic notionsDataDataba

5、se (DB)Database Management System (DBMS) Database System (DBS).Database Administrator (DBA)8Basic NotionsDataDistinct pieces of information represented in a form suitable for processing by computer. Data can exist in a variety of forms - as digital numbers, text, image, sound, video and etc.Database

6、 (DB) In essence, its nothing more than a collection of information that exists over a long period of time.In common parlance, it refers to a collection of data managed by a database management system (DBMS) or just database system (DBS).9Example of Data and Database10DBMSDatabase Management System

7、(DBMS) A collection of programs that enables you to store, modify, and extract information from a database. There are many different types of DBMSs, ranging from small systems that run on personal computers to huge systems that run on mainframes. 11Basic functions of DBMSData definitionAllow creatin

8、g new databases and specify their schema (logical structure of the data), via data definition language (DDL).Data manipulationAllow efficient access to the data, such as querying and modifying the data, via query language or data manipulation language (DML). Operation management of DBSupport the sto

9、rage of very large amounts of data over a long period of time, assuring data integrity, keeping data secure from accident or unauthorized use. Support concurrent, atomic access to data. Creation and maintenance of DBSuch as inputting and transferring of Data, DB backup and recovery, performance moni

10、toring, audit and analysis etc.12Database System (DBS)Database System (DBS).DB, DBMS, Development Tools, DB applications, DB Administrator (DBA) and usersDBOSDBMSDeveloping ToolsDB applicationsUserUserDBAHardwareOperating SystemDBMS, Compiling SystemDeveloping ToolsApplication SystemsDBMS in Compute

11、r System13Database AdministratorDBAPerson who is responsible for management and maintenance of DB.TasksDatabase contents and structuresStorage structure and access methodsDatabase security and integrationMonitor and improve database performance 141.1.2 History of Data managementFile systemsProblems:

12、 limited support to definition of data schema, no directly support to DML (Data Manipulate Language), no support to efficient concurrent, secure access etc.Early DBMSThe first commercial DBMS appeared in the late 1960s, evolved from file systems.The early DBMSs used several data models for describin

13、g structure of DB: hierarchical model and network model.Problems: no support to high-level query languages.15History of Data management (cont.）Relational DBMSA famous paper by Ted Codd in 1970, “A relational model for large shared data banks” in Comm. ACM.Data organized as tables called relations.Un

14、like the user of early DBS, user of a relational system wont be concerned with the storage structure, and queries are expressed in a very high-level language (SQL).Today used in most DBMSs.16Relational ModelBased on tables, such as:acct #namebalance12345Sally1000.2134567Sue285.48 Attributes(column h

15、eaders)Tuples(rows)17Query LanguagesEmployeeNameDeptDepartmentDeptManagerSELECT ManagerFROM Employee, DepartmentWHERE E = Clark Kent”AND Employee.Dept = Department.Dept ;18History of Data ModelData model: abstraction of data features in real world into computer world.Hierarchical model 6

16、0s70s80s90snowRelational modelChoice for most new applicationsObject Bases modelKnowledge Bases modelNetwork model19Relational model or not?Relational model is good for: Large amounts of data simple operationsNavigate among small number of relationsDifficult Applications for relational model:VLSI De

17、sign (CAD in general)CASE: Computer-Aided Software EngineeringGraphical DataWhere number of relations is large, relationships are complexObject Data ModelLogic Data Model20Other Data ModelsObject data modelUsually find objects via explicit navigation, also query language in some systemsComplex Objec

18、ts Nested Structure (pointers or references)Encapsulation, set of Methods/Access functionsObject IdentityInheritance Defining new classes like old classesLogic data modelProlog, DatalogMore power than relational21The DBMS MarketplaceRelational DBMS companies Oracle, Sybase are among the largest soft

19、ware companies in the world.IBM offers its relational DB2 system. With IMS, a nonrelational system, IBM is by some accounts the largest DBMS vendor in the world.Microsoft offers SQL-Server, plus Microsoft Access for the cheap DBMS on the desktop, answered by “l(fā)ite” systems from other competitors.Rel

20、ational companies also challenged by “object-oriented DB” companies.But countered with “object-relational” systems, which retain the relational core while allowing type extension as in OO systems.221.2 Architecture of DBMSMajor components of a DBMSDataMetadataStorage ManagerQuery ProcessorTransactio

21、nManagerSchemaModificationsQueriesModificationsSchema (logical structure of the data); Metadata(data of data)23Architecture of DBSThree Schema Architecture of DBSExternal Schema: user schema or subschemaDefines one view of the data as seen by a specific set of application or end users.There may be m

22、any external schemas in a DB.Schema: conceptual schema, logical schemaDefines data from perspective systems designer; Independent of end users & data storage mechanismThere is only one conceptual schema in a DB.Internal Schema: storage schemaDefines how data is organized, stored and manipulated insi

23、de the system.Totally dependent on particular implementation.There is only one internal schema in a DB.24Three Schema Architecture (cont.)ApplicationAExternal Schema 1SchemaInternal SchemaDBApplicationBApplicationDApplicationEApplicationCExternal Schema 2External Schema 325Independence of Data and P

24、rogramLogical IndependenceVia Reflection of External Schema/SchemaOne Schema corresponds to many External schemas; every Ex-Schema has an Ex-Schema/Schema Reflection.When Schema changes, DBA changes the Ex-Schema/Schema reflections, so application programs neednt been changed.Physical IndependenceVia Reflection of Schema/Inter