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软考总结（1）数据库设计

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Jun 07, 2016 pm 03:16 PM

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数据库设计，是大题中必考的，当然，也是我们开发程序必不可少的，现在对数据库设计进行一下总结。一、数据库设计阶段划分首先，来张图，对数据库的设计流程有一个直观的认识（1）需求分析目标：通过调查研究，了解用户的需求要求和处理要求成果：整理

数据库设计，是大题中必考的，当然，也是我们开发程序必不可少的，现在对数据库设计进行一下总结。

一、数据库设计阶段划分

首先，来张图，对数据库的设计流程有一个直观的认识

软考总结（1）数据库设计

（1）需求分析

目标：通过调查研究，了解用户的需求要求和处理要求

成果：整理形成需求说明书。以后设计的基础和依据。包括：数据库包含的数据、数据的特征、使用频率和数据

量的估计，例如：数据名、类型、数据的要求和使用量的大小等，通常使用数据字典进管理

（2）概念结构设计

目标：对需求分析的数据和要求进行抽象，构造反应用户环境的数据，以及数据之间相互联系的概念模型

（3）逻辑结构设计

目标：根据有关规则，将E-R图转换成关系模式。根据有关规范化的理论确定主键、外键和约束等特性

结果：DBMS所提供的数据定义语言，所写成的数据模式

（4）物理设计

目标：逻辑模型转换成物理模型，包括文件结构、索引等的设计过程

二、E-R模型

软考总结（1）数据库设计

（1）包括：实体、属性、联系、联系的类型（数字）

（2）设计步骤：先设计局部的E-R图，之后进行合并（视图集成）。合并时着力消除各个局部ER图间的不一致

合并时局部ER图的冲突类型：

1）属性冲突：属性域的冲突和属性取值的冲突

2）命名冲突：同名异意，和异名同意

3）结构冲突：同一个对象在不同应用中不同的抽象，同一实体在不图中的属性个数等不完全相同

（3）局部E-R图设计步骤：确定局部视图的范围（例如与采购有有关的），识别局部的每个实体以及实体间的

联系反馈实体以及实体间联系的属性

E-R图向关系模式的转换：

1）一个实体转换为一个关系模式

2）一对一的联系，转化为一个独立的关系模式——属性：联系本身和与之相连的属性的码与任意一

端对应的关系模合并——属性：加入两一个关系的码和另一个关系的属性

3）一对多的关系。可以单独组成一个关系模式——各个实体的码和联系本身的属性。与n端合并——

加入另一端的码和联系本身的属性

4）多对多联系。只能转换为一个独立的关系模式。与联系相连的各个实体的码以及联系本身的属性

5）联系连接多个实体。和前四点相似

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