面向对象系统分析与设计 第八章课件.pptVIP

Chapter 8:Object-Relational Modeling;Chapter Objectives;Chapter Objectives (Continued);父把馆羔舷嫌扔犁凋唤蘸想隘桩铆拎聋虎矮狱愤挡耶效悯筷腿圾碌茅师愤面向对象系统分析与设计 第八章课件面向对象系统分析与设计 第八章课件;Object-relational data modeling converts a conceptual data model to a logical data model based on relational and object-oriented technology.;Purposes of Object-Relational Modeling;What Is a Relational Data Model?;What Is a Relation?;Example relation: note uniqueness of rows guaranteed by Emp_ID. Primary keys are underlined;What Is Normalization?;Consequences of Relations that Are Not Well Structured;The Normal Forms;What Is a Functional Dependency?;Second Normal Form (2NF);This table has a composite key (Emp_ID and Course) Functional dependencies: Emp_ID ? Name, Dept, Salary Emp_ID, Course ? Date_Completed;Solution:;Third Normal Form (3NF);Here, Customer_ID ? Salesperson, and Salesperson ? Region, cause a transitive dependency;Break the relation into two separate relations. 1:N relationship linked by SalesPerson No transitive dependencies Well structured;Primary and Foreign Keys;Referential Integrity;Object-Oriented Extensions to Relational Modeling;Translating Conceptual Data Model to Object-Relational Model;Relational approach, forces atomic attributes;When constructing 1:N relationships, the foreign key is added as an attribute to the relation on the N side.;Associative class and M:N relationship;Points for Figure 8.11;Unary 1:N relationship is represented by a foreign key managerID, which matches with the empId primary key of the same relation.;Unary M:N relationship is represented by a separate relation Prerequisite, whose primary key is composed of two primary key values from the Course relation.;Other Relationships;Merging Object Relationships;Problems with Merging;Recap