数据库课件.ppt

Steps of Database Design Requirement analysis What data, applications, and operations needed Conceptual database design: A high-level description of data, constraints using E - R model or a similar high level data model Logical database design: Convert the conceptual design into a DB schema Schema refinement Normalization of relations: Check relational schema for redundancies and related anomalies. Physical database design : Indexing, clustering and database tuning Create and initialize the database Security design Load initial data, testing Identify different user groups and their roles 面向对象模型 层次模型 网状模型 现实世界 概念模型 （数据模型）逻辑模型 物理模型 信息世界 E-R 图 (E-R模型) 关系模型（表结构） 物理存储结构 数据库的设计步骤 1968, IBM IMS 树型结构 (除根结点外，每个结点有且只有一个双亲结点) DBTG模型 | CODASYL系统 网状结构 (一个结点可有多个双亲，允许多个结点无双亲) Honeywell IDS/2，HP image 机器世界 半结构化数据模型 (1) Entity Relationship Model (实体-联系模型) E-R model of real world Entities (objects) E.g. customers, accounts, bank branch Entities are described by attributes Relationships between entities E.g. Account A-101 is held by customer Johnson Relationship set depositor associates customers with accounts E-R Model is widely used for database design Database design in E-R model usually converted to design in the relational model . Was first proposed by Pete Chen. Relationship Entity Attribute Attribute Entity-Relationship Model (Cont.) Example of schema in the entity-relationship model (2) Relational Model Example of tabular data in the relational model customer- name Customer-id customer- street customer- city Johnson Smith Johnson Jones Smith 192-83-7465 019-28-3746 192-83-7465 321-12-3123 019-28-3746 Alma North Alma Main North Palo Alto Rye Palo Alto Harrison Rye Attributes Tuple 元组 Column ( field ) Relation Customer schema Transfer E-R diagrams into relational schema A Sample Relational Database Another example: University Database Sid Sname Ssex Sage sdept 3023001093 Tom M 21 Cs 3011112340 Mary F 20 Cs 3020621034 Jack M 18 Cs 3020831035 Smith M