资料讲稿数据库概论.pptxVIP

第9章 数据库设计;2;9.1 数据库设计概述;4;数据库设计的基本任务;;;9.1 数据库设计概述;9;10;11;9.2 数据库设计的需求分析;Figure: Types of Things;Relationships among Things;Important to know the number of associations of things the cardinality (基数) or multiplicity of the relationship one to one, one to many, many to many Also may be important to know the range of possible values of the cardinality zero to one, zero to many: optional relationship（可选关系） one to one, one to many: mandatory relationships（强制关系）;Binary relationship (二元联系) Relationship between two different types of things Unary (recursive) relationship (一元联系) Relationship between two things of the same type Ternary relationship (三元联系) A relationship between three different types of things n’ary relationship (多元联系) A relationship between n (any number) different types of things;Attribute: one piece of specific information about a thing a customer has a name, phone number, credit limit etc Identifier (key): an attribute that uniquely identifies a thing a person’s social insurance number, or an invoice, or transaction number Compound attribute: an attribute that contains a collection of related attributes a full name is made up of first and last name;Data Entities The things the system needs to store information about in the traditional approach Computer processes interact with these data entities Objects – the other way to look at things Similar to data entities in traditional approach BUT the objects do the work in the system, they do not just store information (They have behavior);19;20;21;22;23;24;25;26;27;28;29;30;31;32;33;34;35;36;37;38;39;40;41;42;9.3 数据库的概念设计;44;45;46;47;48;49;50;51;52;53;54;55;56;57;58;59;60;61;62;63;64;65;66;67;68;69;70;71;72;73;74;75;76;77;78;79;80;81;82;83;84;85;86;87;88;89;90;数据库逻辑设计案例;数据库设计的综合案例;93;94;95;96;97;98;99;100;101;102