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27 fcs157al1 (1)

  1. 1. Chapter 1 The Worlds1 of Database Systems File Systems and Databases Prof. Sin-Min Lee Dept. of Computer Science
  2. 2. 1 Tuesday Thursday 10:15 – 11:30
  3. 3. Your evaluation in this course is determined by: 30%1Class PresentationPresentation report 10% 5% ??!
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  7. 7. GOOD REFERENCE A. Silberschatz, H.F. Korth, S. Sudarshan: Database System Concepts, 5th Ed., McGraw-Hill, 2006.1
  8. 8. The mediocre teacher tells. The good teacher explains.1 The superior teacher demonstrates. The great teacher inspires.
  9. 9. Files and Databases File: A collection of records or documents dealing with one organization, person, area or subject (Rowley)1 Manual (paper) files Computer files Database: A collection of similar records with relationships between the records (Rowley) Bibliographic, statistical, business data, images, etc.
  10. 10. Introducing the Database Major Database Concepts1 Data and information Data - Raw facts Information - Processed data Data management Database Metadata Database management system (DBMS)
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  13. 13. Sales per Employee for Each of ROBCOR’S Two Divisions1 Figure 1.1
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  15. 15. Database Systems Types of Database Systems Number of Users1 Single-user – Desktop database Multiuser – Workgroup database – Enterprise database Scope Desktop Workgroup Enterprise
  16. 16. Database Systems Types of Database Systems Location1 Centralized Distributed Use Transactional (Production) Decision support Data warehouse
  17. 17. Database A Database is a collection of stored operational data used by the application systems of some particular enterprise (C.J. Date)1 Paper “Databases” Still contain a large portion of the world’s knowledge File-Based Data Processing Systems Early batch processing of (primarily) business data Database Management Systems (DBMS)
  18. 18. Why DBMS? History 50’s and 60’s all applications were custom built for particular needs1 File based Many similar/duplicative applications dealing with collections of business data Early DBMS were extensions of programming languages 1970 - E.F. Codd and the Relational Model 1979 - Ashton-Tate and first Microcomputer DBMS
  19. 19. File Based Systems Application File Delivery1 Toys List Addresses Coal Estimation Naughty Just what asked for Nice Toys
  20. 20. From File Systems to DBMS Problems with file processing systems Inconsistent data1 Inflexibility Limited data sharing Poor enforcement of standards Excessive program maintenance
  21. 21. DBMS Benefits Minimal data redundancy Consistency of data1 Integration of data Sharing of data Ease of application development Uniform security, privacy, and integrity controls Data accessibility and responsiveness Data independence Reduced program maintenance
  22. 22. Terms and Concepts Data independence Physical representation and location of data and the use of that data are separated1 The application doesn’t need to know how or where the database has stored the data, but just how to ask for it Moving a database from one DBMS to another should not have a material effect on application program Recoding, adding fields, etc. in the database should not affect applications
  23. 23. Database Environment1 CASE Tools User Interface Application Programs Repository DBMS Database
  24. 24. Database Components DBMS =============== Design tools1 Table Creation Form Creation Query Creation Report Creation Application Procedural Database language Programs compiler (4GL) ============= Run timeDatabase contains: Form processorUser’s Data Query processor UserMetadata Report Writer InterfaceIndexes Language Run time ApplicationsApplication Metadata
  25. 25. Types of Database Systems PC databases Centralized database1 Client/server databases Distributed databases Database models
  26. 26. PC Databases E.g.: Access1 FoxPro Dbase Etc.
  27. 27. Centralized Databases1 Central Computer
  28. 28. Client Server Databases Client1Client Network Database Server Client
  29. 29. Distributed Databases Location B Location C1 computer computer Homogeneous computer Databases Location A
  30. 30. Distributed DatabasesHeterogeneous ClientOr Federated RemoteDatabases Comp. 1DatabaseServer Local Network Comm Server Remote Client Comp.
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  34. 34. Introducing the Database Importance of DBMS It helps make data management more efficient1 and effective. Its query language allows quick answers to ad hoc queries. It provides end users better access to more and better-managed data. It promotes an integrated view of organization’s operations -- “big picture.” It reduces the probability of inconsistent data.
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  36. 36. The DBMS Manages the Interaction Between the End User and the Database1 Figure 1.2
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  38. 38. Introducing the Database Why Database Design Is Important? A well-designed database facilitates data1 management and becomes a valuable information generator. A poorly designed database is a breeding ground for uncontrolled data redundancies. A poorly designed database generates errors that lead to bad decisions.
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  43. 43. Historical Roots Why Study File Systems? It provides historical perspective.1 It teaches lessons to avoid pitfalls of data management. Its simple characteristics facilitate understanding of the design complexity of a database. It provides useful knowledge for converting a file system to a database system.
  44. 44. Contents of the CUSTOMER File1 Figure 1.3
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  47. 47. Table 1.1 Basic File Terminology Data “Raw” facts that have little meaning unless they have been organized in some logical manner. The smallest piece of data that can be “recognized” by the computer is a single character, such as the letter A, the number 5, or some1 symbol such as; ‘ ? > * +. A single character requires one byte of computer storage. Field A character or group of characters (alphabetic or numeric) that has a specific meaning. A field might define a telephone numbers, a birth date, a customer name, a year-to-date (YTD) sales value, and so on. Record A logically connected set of one or more fields that describes a person, place, or thing. For example, the fields that comprise a record for a customer named J. D. Rudd might consist of J. D. Rudd’s name, address, phone number, date of birth, credit limit, unpaid balance, and so on. File A collection of related records. For example, a file might contain data about ROBCOR Company’s vendors; or, a file might contain the records for the students currently enrolled at Gigantic University.
  48. 48. Contents of the AGENT File1 Figure 1.4
  49. 49. A Simple File System1 Figure 1.5
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