1,Database Systems 数据库系统,衷宜 zhongyimail.njust.edu.cn 计算机科学与技术学院,2,Database systems,教学目标： 掌握关系数据库设计（包括数据库概念建模和关系数据库模型的设计）和编程（包括关系模型代数运算和数据库语言SQL）的基本概念和原理； 掌握数据库设计和编程的一般过程和基本方法； 能自主开发和维护简单的数据库系统； 提高专业英文资料的查阅能力,3,Database systems,教材Jeffrey D.Ullman, Jennifer Widom. A first course in database systems. 机械工业出版社，2008. 参考资料 Jeffrey D.Ullman, Jennifer Widom. 数据库系统基础教程. 岳丽华译. 机械工业出版社，2003. Abraham Silberschatz, Henry E Korth, S.Sudarshan. Database System Concepts. 机械工业出版社 http:/www-db.stanford.edu/ullman/fcdb.html,4,Database systems,教学安排： 48 hours Classroom teaching 40 hours Practice 8 hours 考查方式： Final exam 70% Homework 15% Project 15%,5,1 The Worlds of Database Systems,The Evolution of Database Systems Overview of a DBMS Outline of Database System Studies,6,1.1 The Evolution of Database Systems,Whats a database?,In essence, a database is a collection of information that exists over a long period of time, often many years.,7,1.1 The Evolution of Database Systems,Database Applications: Universities: registration, grades Airlines: reservations, schedules Banking: all transactions Sales: customers, products, purchases Online retailers: order tracking, customized recommendations Manufacturing: production, inventory, orders, supply chain Human resources: employee records, salaries, tax deductions Databases touch all aspects of our lives,8,1.1 The Evolution of Database Systems,In the early days, database applications were built directly on top of file systems.,9,1.1 The Evolution of Database Systems,Drawbacks of using file systems to store data: Data redundancy and inconsistency Multiple file formats, duplication of information in different files Difficulty in accessing data Need to write a new program to carry out each new task Data isolation multiple files and formats,10,1.1 The Evolution of Database Systems,Integrity problems Integrity constraints (e.g. account balance 10) become “buried” in program code rather than being stated explicitly Hard to add new constraints or change existing ones,11,1.1 The Evolution of Database Systems,演示,12,1.1 The Evolution of Database Systems,Atomicity of updates Failures may leave database in an inconsistent state with partial updates carried out Example: Transfer of funds from one account to another should either complete or not happen at all,13,1.1 The Evolution of Database Systems,演示,14,1.1 The Evolution of Database Systems,Concurrent access by multiple users Concurrent accessed needed for performance Uncontrolled concurrent accesses can lead to inconsistencies Example: Two people reading a balance and updating it at the same time,15,1.1 The Evolution of Database Systems,演示,16,1.1 The Evolution of Database Systems,Security problems Hard to provide user access to some, but not all, data,17,1.1 The Evolution of Database Systems,Database systems offer solutions to all the above problems,18,1.1 The Evolution of Database Systems,Late 1960s and 1970s: Network and hierarchical data models in widespread usea network data model,19,1.1 The Evolution of Database Systems,a hierarchical data model,20,1.1 The Evolution of Database Systems,1970s: Ted Codd (August 23, 1923 April 18, 2003) defines the relational data model Received the ACM Turing Award in 1981 IBM Research begins System R prototype UC Berkeley begins Ingres prototype,21,1.1 The Evolution of Database Systems,1980s: Research relational prototypes evolve into commercial systems SQL becomes industrial standard Parallel and distributed database systems Object-oriented database systems,1990s: Large decision support and data-mining applications Large multi-terabyte data warehouses Emergence of Web commerce,2000s: XML and XQuery standards Automated database administration,22,1.2 Overview of a DBMS,A DBMS is a powerful tool for creating and managing large amounts of data efficiently and allowing it to persist over long periods of time, safely. In common, a database is a collection of data that is managed by a database management system (DBMS, database system).,23,1.2 Overview of a DBMS,A DBMS is expected to:,Data Definition Language (DDL): create database and specify their schema.A schema is a group of collections of sentences that are expressed by DDL to describe the logical structure of some database completely.,Data Query Language and Data Manipulation Language: query and modify the data based on the schema of the database.,The storage of very large amounts of data: many terabytes or more, over a long period of time, allowing efficient access.,24,1.2 Overview of a DBMS,A DBMS is expected to (cont.):,Enable durability: the recovery of the database in the face of failures, errors of many kinds, or intentional misuse.,Data sharing: access to data from many users at once; without allowing the action of one user to affect other users; without actions on the data to be performed partially but not completely.,25,1.2 Overview of a DBMS,演示,26,1.2 Overview of a DBMS,27,Database management system components,