第二章介绍数据库应用系统的设计过程，重点介绍ER模型以及ER模型到关系模型的转换规则，反过来ER和关系模型是服务数据库的设计过程的。 数据库系统生存期前期先规划，然后进行设计，对数据库的物理设计初步评价完成后就可以开始建立数据库了。先是构建，然后
第二章介绍数据库应用系统的设计过程，重点介绍ER模型以及ER模型到关系模型的转换规则，反过来ER和关系模型是服务数据库的设计过程的。
数据库系统生存期前期先规划，然后进行设计，对数据库的物理设计初步评价完成后就可以开始建立数据库了。先是构建，然后装载数据，之后是不断地进行调试，运行再调试，当然，数据库后期维护是必要的。
ER模型其实有三个只要元素，实体、联系和属性，实体和实体之间有联系，实体和联系又有属性。
关系模型用二维表格表示实体集，用关键码表示实体之间联系。
对于本章的知识点，我将自己的全部理解全都倾注到了图上，相信大家一眼就看明白了知识点之间的联系。
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