东南大学数据库课程01-数据库原理及应用引言

数据库原理及应用 引言

目录

• 数据库原理及应用 引言
• Introduction
• Data,DataModel and Data Schema
• Levels of Abstraction(三级抽象)
• Data Indepence（数据独立性）
• The History of Database Technology and its Classification
• DataBase System and its Life Cycle

Introduction

• What’s a database?

  • A very large, integrated collection of data
  • Models real-world enterprise.
    • Entities (e.g., students, courses)
    • Relationships (e.g., electives)

• What’s a DBMS?

  Database Management System: a software package designed to store and manage databases

• Why use DB instead of File?

  • Special code for different queries（File just a char flow）
  • data inconsistency due to multiple concurrent users
  • Security and access control
  • Crash recovery

Data,DataModel and Data Schema

• data 数据：真实世界的描述，信息的存在实体
• datamodel 数据模型：用来描述数据的一组概念和定义集（c语言语法）
• schema 数据模式：对于一组数据，数据模型的一个具体实现（c语言程序）

Levels of Abstraction(三级抽象)

• Physical Schema：数据库数据在计算机的底层存储（文件，二进制数…）
• Conceptual Schema：数据库用户在数据库中定义的数据的逻辑结构（关系模型中的表）
• View：用户看到的数据（为了数据的访问安全，我们并不希望用户看到所有数据，所以可以做一张视图，里面列出用户能看的数据，给用户看）

💡 Physical Schema 和 Conceptual Schema只有一份 View根据用户需求有多份，View只有定义，临时计算，没有实体

Data Indepence（数据独立性）

数据库的三层抽象带来了两级隔离

• 应用无需关心数据如何组织和存储
• logical data Independence：Protection from changes in logical structure of data.
• Physical data independence: Protection from changes in physical structure of data.

The History of Database Technology and its Classification

• 1. According to the development of data model
  • No management: just used for scientific computing
  • File System: Simple data management
  • Demand of data management growing constinuously, DBMS emerged

• According to the development of DBMS architectures

  • Centralized database systems
  • Parallel database systems
  • Distributed database systems (and Federated database systems)
  • Mobile database systems

• According to the development of architectures of application systems based on databases

  • Centralized structure : Host＋Terminal

  • Distributed structure

  • Client/Server structure（CS模式）

    

  • Three tier/multi-tier structure（前后端分离）

    

    用户机器只需要能运行一个浏览器即可，且无需安装客户端

  • Mobile computing

  • Grid computing / Cloud computing

• According to the expanding of application fields

  • OLTP（联机事物处理，相对于OLAP联机分析处理而言）
  • Engineering Database
  • Deductive Database
  • Multimedia Database
  • Temporal Database
  • Spatial Database
  • Data Warehouse, OLAP, Data Mining
  • Knowledge Management
  • … …

DataBase System and its Life Cycle