tailieunhanh - Database System: Chapter 1 - Introduction

Database System: Chapter 1 - Introduction presents about File based approach, Database approach, Basic definitions, Database systems concepts (Data model, Three schema architecture – Data independence, DBMS languages, Classification of DBMS, Database users). | Chapter 1 Introduction Outline Introduction File based approach Database approach Basic definitions Database systems concepts Data model Three schema architecture – Data independence Database schema – state – instance DBMS languages Classification of DBMS Database users Slide 1- File-based Approach Data is stored in one or more separate computer files Data is then processed by computer programs - applications Slide 1- File-based Approach Slide 1- File-based Approach Problems/Limitations Data Redundancy Data Inconsistency More details: see [2] Slide 1- File-based Approach Shared File Approach Data (files) is shared between different applications Data redundancy problem is alleviated Data inconsistency problem across different versions of the same file is solved Other problems: Rigid data structure: If applications have to share files, the file structure that suits one application might not suit another Physical data dependency: If the structure of the data file needs to | Chapter 1 Introduction Outline Introduction File based approach Database approach Basic definitions Database systems concepts Data model Three schema architecture – Data independence Database schema – state – instance DBMS languages Classification of DBMS Database users Slide 1- File-based Approach Data is stored in one or more separate computer files Data is then processed by computer programs - applications Slide 1- File-based Approach Slide 1- File-based Approach Problems/Limitations Data Redundancy Data Inconsistency More details: see [2] Slide 1- File-based Approach Shared File Approach Data (files) is shared between different applications Data redundancy problem is alleviated Data inconsistency problem across different versions of the same file is solved Other problems: Rigid data structure: If applications have to share files, the file structure that suits one application might not suit another Physical data dependency: If the structure of the data file needs to be changed in some way, this alteration will need to be reflected in all application programs that use that data file No support of concurrency control: While a data file is being processed by one application, the file will not be available for other applications or for ad hoc queries Slide 1- Database Approach Arose because: Definition of data was embedded in application programs, rather than being stored separately and independently No control over access and manipulation of data beyond that imposed by application programs Result: The Database and Database Management System (DBMS). Slide 1- Database Approach Slide 1- Slide 1- Basic Definitions Database: A collection of related data. Data: Known facts that can be recorded and have an implicit meaning. Mini-world: Some part of the real world about which data is stored in a database. For example, student grades and transcripts at a university. Database Management System (DBMS): A software package/ system to facilitate .