数据库系统原理英.ppt
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1、Chapter 1 IntroductionFebruary 20111Database System Concepts-Chapter1 Introduction-Main Parts in This ChapternDatabase System ApplicationsnPurpose of Database SystemsnView of DatanDatabase Languages nRelational DatabasenDatabase DesignnData Storage and Querying nTransaction Management nDatabase Arch
2、itecturesnDatabase Users and AdministratorsnHistory of Database SystemsnAppendix:Data,Information,Knowledge,etc.February 20112Database System Concepts-Chapter1 Introduction-1.0 DB,DBMS,DBSnDefinitions in the textbooknDatabase(DB)a collection of interrelated data,stored in systems as files nDatabase
3、management system(DBMS)DB,or a collection of interrelated data set of programs to access the data in DBnDatabase system(DBS)nhaving the same definition as DBMS in the textbooknthe term DBS and DBMS are used interchangeably in the textbookFebruary 20113Database System Concepts-Chapter1 Introduction-1
4、.0 DB,DBMS,DBS(cont.)nDBMS provides an environment that is both convenient and efficient for store and retrieve information ndefinition of structures for storage of informationndata manipulation mechanismsndata safety mechanismsnDefinitions in some other textbooksnFig.1.0.1 nDatabase(DB)a collection
5、 of interrelated data,stored in systems as filesFebruary 20114Database System Concepts-Chapter1 Introduction-1.0 DB,DBMS,DBS(cont.)nDefinitions in some other textbooks(cont.)nDatabase management system(DBMS)a system/mechanism to manage data in DB or:set of programs to access the data in DBnDatabase
6、system(DBS)DB+DBMS+Users/AdministersnDatabase application system DB+DBMS+Application programs+Users/AdministersFebruary 20115Database System Concepts-Chapter1 Introduction-DBMSApplication program 1DB fileDB query language e.g.SQLAPI,e.g.ODBC,JDBCUsersDBMSDBDBS/DBASFig.1.0.1 DBS and DBASApplication p
7、rogram 1February 20116Database System Concepts-Chapter1 Introduction-nDatabases and DBS touch all aspects of our livesnBanking:all transactionsnAirlines:reservations,schedulesnUniversities:registration,gradesnSales:customers,products,purchasesnManufacturing:production,inventory,orders,supply chainnH
8、uman resources:employee records,salaries,tax deductions1.2 Purpose of Database SystemsFebruary 20117Database System Concepts-Chapter1 Introduction-nIn the early days,data management applications were built on top of file systemsnE.g.Saving-bank enterprisena number of application programs to access d
9、ata filesnA program to debit(将.记入借方)or credit(将.记入贷方)an account(帐户)nA program to add a new accountnA program to find the balance(收付差额,余额)of an accountnA program to generate monthly statements1.2 Purpose of Database Systems(cont.)February 20118Database System Concepts-Chapter1 Introduction-nData mana
10、gement on the basis of file systemsnExample customer_record=in Customer_FilenFS access needs file name,item name,length of record,length of item,position of item in the record,storage structure,access method,.nDemerit application programs are not independent of the file system(or operating system)de
11、pendency among application programs and data(程序与数据的非独立/依存性)1.2 Purpose of Database Systems(cont.)February 20119Database System Concepts-Chapter1 Introduction-Fig.1.0.2 Why DBS neededsecondary storage (e.g.disk,tape)and data on it (address:cylinder,track,sector)memory controllers(i.e.disk controller)
12、,on the basis of secondary storages physical structures,such as storage structures,access method access programs(I)direct accessthrough disk controller(I)access through OS file system(II)access through data base system(DBS)(III)access programs(II)access programs (III)I/O system:driversfile system:fi
13、les logical structures and access methodsDBMS:relational tables logical structures and access methods system calls related to file management DBS API February 201110Database System Concepts-Chapter1 Introduction-Select NameFrom Student Where S#=100DBSlogicalstructures:relations/tuplesDBMSDB userLogi
14、cal address:#RecordRecord1Recordkblock1OS:Logical fileRecordiRecordmBlock nPhysical address:platter/track/sectorblock1blockiblockkPhysical File on diskDB filesblockOS:file system and I/O subsystem view of data model view of fileFig.1.0.3 Database access February 201111Database System Concepts-Chapte
15、r1 Introduction-nDrawbacks of using file systems to store datandata redundancy(冗余)and inconsistency(不一致性)nmultiple file formats,duplication(副本)of information in different filesndifficulty in data accessnneed to write a new program to carry out each new taskndata isolation(独立性)nmultiple files and for
16、mats1.2 Purpose of Database Systems(cont.)February 201112Database System Concepts-Chapter1 Introduction-nintegrity(完整性)problemsndata values should satisfy consistency constraintsnintegrity constraints (e.g.customer_age 0)become part of program codenhard to add new constraints or change existing ones
17、natomicity problemsnfailures may leave database in an inconsistent state with partial updates carried outne.g.transfer of funds from one account to another should either complete or not happen at all1.2 Purpose of Database Systems(cont.)February 201113Database System Concepts-Chapter1 Introduction-n
18、concurrent access anomaliesnuncontrolled concurrent accesses can lead to inconsistenciesne.g.two persons read an account and update it at the same timensecurity problemsnDatabase systems offer solutions to all the above problems1.2 Purpose of Database Systems(cont.)February 201114Database System Con
19、cepts-Chapter1 Introduction-1.3 View of DatanBasic concepts in DBS theorynview of data(数据视图),data abstractndata model,data schema(模式),schema instancenlogical/physical isolation1.3.1 Data abstraction nData Viewn data features from some viewpointsn e.g.about student,his name,sex,age,.nTo simplify and“
20、divide and conquer”the design of complex data application systems ndescribes/design application data in three levels,and obtains three types of schemaFebruary 201115Database System Concepts-Chapter1 Introduction-Fig.1.1 The three levels of data abstractionFebruary 201116Database System Concepts-Chap
21、ter1 Introduction-nView levelndescribe data from nhow the data items in DB are used by different usersnseveral views for one datum ndescription resultsnexternal schema(外模式)=view,set of viewsndescription procedure/Logical DB designnview abstractionnmerits:application programs are programmed according
22、 to views.Views can also hide information(e.g.,salary)for security purposes.1.3.1 Data abstraction(cont.)February 201117Database System Concepts-Chapter1 Introduction-nE.g.Banking Application Areas in Fig.6.25 in page 240nfrom more than one viewpoints,view integrationn view1:customer view2:customer
23、view3:customer view4:loan view5:account view6:.1.3.1 Data abstraction(cont.)February 201118Database System Concepts-Chapter1 Introduction-nLogical levelnimplementation-oriented,describes how the data items are stored in DBS(e.g.as relational tables),and what relationships exist among those data:tabl
24、e customername:string;street:string;city:integer;ndescription resultsnlogical schema(逻辑模式),e.g.relational tables ndescription procedure/Logical DB designnlogical abstractionnMerits:hiding physical implementation details1.3.1 Data abstraction(cont.)February 201119Database System Concepts-Chapter1 Int
25、roduction-nPhysical levelndescribes how the data(e.g.,customer record/table)are actually stored in files(or in secondary storage)ndescription resultsnphysical/internal schema(物理模式,内模式)ni.e.storage structure and access methods,such as index,physical blocks,access methods for secondary memory,etc.ndes
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