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    河北二十选五最新开奖:浙江大学数据库系统概念PPT第一章,对应原版教材第五版.ppt 30页

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    Database system Introduction What is Database Systems? Purpose of Database Systems Data Abstraction Database Languages Database Users Database System Structure Application Architectures History of Database Systems Database System Database System Database DBMS Database : Collection of interrelated data (information about a particular enterprise) Large amount of information (data) Well organized: Definition and Manipulation Share among several users, avoid possible anomalous results Safety of the information stored, despite system crash or unauthorized access DBMS is a software: Set of programs to access the data Be able to manage databases. Provides an environment that is both convenient and efficient to use. Database Applications Database touch all aspects of our lives Banking: all transactions Airlines: reservations, schedules Universities: registration, grades Sales: customers, products, purchases Manufacturing: production, inventory, orders, supply chain Human resources: employee records, salaries, tax deductions Use of database grew last four decades Very few people interacted directly with database system, custom did not know the backend database, they got printed report, etc. Some customs access system via phone interface. Direct user access via Internet. The purpose of the course is to understand the fundamental of Database System. How to use DBMS. (included) How DBMS works. ( A brief introduction ) Purpose of Database Systems In the early days, database applications were built on top of file 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 Integrity problems Integrity constraints (e.g. account balance > 0) become part of program code Hard to add new constraints or change existing ones Purpose of Database Systems (C

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