3 The Relational Model(对应书第4章).pdfVIP

Chapter 3 The Relational Model 四川大学计算机（软件）学院 龚勋 Agenda 3.1 Background 3.2 Relational Model 3.3 Relational Data Structure 3.4 Relation Integrity 关系完整性 3.5 Views 视图：（基本）关系和视图的 区别 3.1 Background The relational Database Management System (RDBMS) has become the dominant data-processing software in use today. 关系数据库管理系统基于关系模型实现 Brief history of the Relational Model E.F.Codd “A Relational Model of Data for Large Shared Data Banks” 大型共享数据库数 据的关系模型 IBM RDBMS System R 第一个商品DBMS Ingres, IBM DB2, Oracle, Sybase, MS SQL Server… 3.2 Relational Model Data Model 数据模型（参见2.3节） An integrated collection of concepts for describing and manipulating data, relationships between data, and constraints on data in an organization. A data model can be thought of as comprising three components: 一个数据模型包含三要素（三 个组件） Data structure 数据结构（PPT的3.2.1节） Data manipulation 数据操纵（PPT的第4章） Constraints of data integrity 数据的完整性 约束（PPT的3.3节） 3.2 Relational Model The Relational Model (Codd 1976) is currently the most popular model for database systems. The simplest and most uniform data structure: data are stored in tables 最简单的结构 用二维表存储数据 The most formal of all data models. It is based on the mathematical concept of a relation in set theory: a table is a relation 集合论为理论基础 3.3 Relational Data Structure 关系数据模型的结构由关系来定义 Relation 关系： A relation is a table with columns and rows. 一个关系 一张二维表 只应用到逻辑结构（外部层和概念层） 由属性、域和元组定义 Relational database 关系数据库 A collection of normalized relations with distinct relation names. 其 集 合 3.3.1 Relation schema and Relation Database schema Relation schema 关系模式（关系框架） A named relation defined by a set of attribute and domain name pairs. 对型的描述 （关系模式 是型，关系是值） 关系R的模式定义：(A1:D1,A2:D2,…,An:Dn) Relational database schema 关系数据库 模式 A set of relation schemas, each with a distinct names. 其 集 合 关系模型和模式的区别 属性名 属性的取值范围 83.3.2 Relation 关系 Relation 关系由属性、域和元组定义： Attribute (columns, field) 属性（列，字段）： An attribute is a named column of a relation. Domain 域：属性的取值范围 A domain is the s