Insulationbetweenprogramsanddata:Calledprogram-dataindependence.AllowschangingdatastoragestructuresandoperationswithouthavingtochangetheDBMSaccessprograms. DataAbstraction:Adatamodelisusedtohidestoragedetailsandpresenttheuserswithaconceptualviewofthedatabase. Supportofmultipleviewsofthedata:Eachusermayseeadifferentviewofthe...
外文翻译数据库-DATABASE MANAGEMENT SYSTEMS(DBMS)AND MANAGEMENT INFORMATION SYSTEM(MIS) 热度: Architecture of a Database System 热度: DATABASE MANAGEMENTSYSTEM ARCHITECTURE ThelogicalDBMSarchitecture ThephysicalDBMSarchitecture DBMSARCHITECTURE ThelogicalDBMSarchitecture ...
(say 100) and updating it by withdrawing money (say 50 each) at the same time Security problems Hard to provide user access to some, but not all, data Database systems offer solutions to all the above problems Levels of Abstraction Physical level: describes how a record (e.g., customer...
Database system concepts PPT DatabaseConceptSystems 李楠(SophiaLi)lin@zucc.edu.cn DatabaseSystemConcepts-5thEdition,May23,2005 1.1 ©Silberschatz,KorthandSudarshan CourseIntroduction Agenda:Why?What?How?FinalResult!!!AdministrativeInformation DatabaseSystemConcepts-5thEdition,May23,2005...
Levels of a DBMS Logical Level abstraction of the real world as it pertains to the users of the database DBMS provides a DDL to describe the logical schema in terms of a specific data model such as relational, hierarchical, network, or inverted list ...
APhysical Data Modeldescribes a database-specific implementation of the data model. It offers database abstraction and helps generate the schema. This is because of the richness of meta-data offered by a Physical Data Model. The physical data model also helps in visualizing database structure by...
LevelsofAbstraction nPhysicallevel:describeshowarecord(e.g.,customer)isstorednLogicallevel:describesdatastoredindatabase,andthe relationshipsamongthedata.typeinstructor=recordID:string;name:string;dept_name:string;salary:integer;end;nViewlevel:applicationprogramshidedetailsofdatatypes.Viewcanalsohideinformation(...
object types and collection types. An object type UDT is a templatized abstraction of some real-world entity and a collection data type is a data unit consisting of an indefinite number of elements of the same data type. Differentschemaobjects can reference these UDTs in ORDBMSes. By defining...
Minimum and maximum cardinalities are also specified in the E-R data model Different notations are used in E-R data model to represent cardinalities Cardinalities slide Enhanced E-R data model adds the additional features in the E-R data model Supertype/subtype relationship also called gen/spec ...
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