数据库系统概念第六版笔记

Abraham Siberschatz Henry E Korth S.Sudarshan 杨冬青 李红艳 唐世渭等译。

华章一套书的标志性语言是:

文艺复兴以降,源远流长的科学精神和逐步形成的学术规范,使西方国家在自然科学的各个领域取得了垄断性的优势;也正是这样的传统,使美国在信息技术发展的六十多年间名家辈出、独领风骚。

数据库管理系统:DBMS (DataBase-Management System)是一个互相关联的数据的集合和一组用以访问这些数据的程序组成。这个数据集合通常称作数据库(DataBase).

数据孤立:data isolation

完整性问题:integrity problem

原子性问题:atomicity problem:一旦故障发生,数据就应被恢复到故障发生以前的一致状态。

并发访问异常:concurrent-access anomaly:允许多个用户同时更新数据。

安全性问题: security problem

实例:特定时刻存储在数据库中的信息的集合称作数据库的一个实例I(instance).数据库的总体设计称作数据库的模式(schema).

数据模型:data model

*关系模型:relational model :用表的集合来表示数据和数据间的联系。

*实体-联系模型(entity-relationship):认为现实世界由一组实体的基本对象以及这些对象见的联系构成。

*基于对象的数据模型(object-based data model):可以看成是E-R模型增加了封装、方法和对象标识等概念后的扩展。

 

转载于:https://www.cnblogs.com/jzzgci/p/3222152.html

数据库系统概念(杨冬青)习题答案Chapter 1 provides a general overview of the nature and purpose of database systems. The most important concept in this chapter is that database systems allow data to be treated at a high level of abstraction. Thus, database systems differsignificantly from the file systemsand general purpose programming environments with which students are already familiar. Another important aspect of the chapter is to provide motivation for the use of database systems as opposed to application programs built on top of file systems. Thus, the chapter motivates what the student will be studying in the rest of the course. The idea of abstraction in database systems deserves emphasis throughout, not just in discussion of Section 1.3. The overview of the structure of databases is, of necessity, rather brief, and is meant only to give the student a rough idea of some of the concepts. The student may not initially be able to fully appreciate the concepts described here, but should be able to do so by the end of the course. The specifics of the E-R, relational, and object-oriented models are covered in later chapters. These models can be used in Chapter 1 to reinforce the concept of abstraction, with syntactic details deferred to later in the course. If students have already had a course in operating systems, it is worthwhile to point out how the OS and DBMS are related. It is useful also to differentiate between concurrency as it is taught in operating systems courses (with an orientation towardsfiles, processes,and physical resources)and database concurrency control (with an orientation towards granularity finer than the file level, recoverable transactions, and resources accessed associatively rather than physically). If students are familiar with a particular operating system, that OS’s approach to concurrent file access may be used for illustration.
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