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Preparing for BIT – IT2301 Database Management Systems 2001b


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Preparing for BIT – IT2301 Database Management Systems, on Rupavahini by Gihan Wikramanayake, 03rd May 2001, 2200-2215 hrs.

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Preparing for BIT – IT2301 Database Management Systems 2001b

  1. 1. IT2301 Database Management Systems [email_address] PREPARING FOR THE BIT Preparing for BIT 03/05/2001
  2. 2. Today’s Agenda <ul><li>Two Modules for Semester 2 </li></ul><ul><ul><li>Database Management Systems </li></ul></ul><ul><ul><li>Fundamentals of Software Engineering </li></ul></ul>
  3. 3. BRIEF SYLLABUS <ul><li>TOPIC MIN. NO. OF HOURS </li></ul><ul><li>1. File Organisation ... 12 </li></ul><ul><li>2. Introduction to DBMS 06 </li></ul><ul><li>3. Data Model 04 </li></ul><ul><li>4. Database Design Process 11 </li></ul><ul><li>5. Data Normalisation process ... 03 </li></ul><ul><li>6. Data Manipulation 24 * </li></ul>
  4. 4. BRIEF SYLLABUS cont. <ul><li>TOPIC MIN. NO. OF HOURS </li></ul><ul><li>2. Introduction to DBMS 06 </li></ul><ul><ul><li>a. The Evolution of Database Technology 02 </li></ul></ul><ul><ul><li>b. Database Architecture 04 </li></ul></ul>
  5. 5. Introduction to DBMS - OBJECTIVES <ul><li>Define the following key terms: Data, information, database, database system, database management system </li></ul><ul><ul><li>DATABASE - A collection of interrelated data items that can be processed by one or more application systems. </li></ul></ul>AFTER SUCCESSFULLY COMPLETING THIS SECTION STUDENTS SHOULD BE ABLE TO:
  6. 6. Introduction to DBMS - OBJECTIVES <ul><li>List and briefly describe components of a typical database environment </li></ul><ul><li>Explain how four components hardware , software , data and people work together to form today’s database systems. </li></ul>AFTER SUCCESSFULLY COMPLETING THIS SECTION STUDENTS SHOULD BE ABLE TO:
  7. 7. Introduction to DBMS - OBJECTIVES Computer Terminals Printer DBMS Application Program Database Data Dictionary/Directory User Programmer/Analyst Administrator hardware, software, data and people
  8. 8. Introduction to DBMS - OBJECTIVES cont. <ul><li>Discuss data sharing in an organisation between different functional areas, management levels and geographical locations </li></ul>
  9. 9. Introduction to DBMS - OBJECTIVES cont. <ul><li>Briefly describe the evolution of database systems </li></ul><ul><li>Origins goes back to 1950s. Technology used for popular commercial data management products: </li></ul><ul><ul><ul><li>Conventional File Systems - flat file </li></ul></ul></ul><ul><ul><ul><li>Hierarchical Data Model </li></ul></ul></ul><ul><ul><ul><li>Network Data Model </li></ul></ul></ul><ul><ul><ul><li>Relational Data Model </li></ul></ul></ul>
  10. 10. Introduction to DBMS - OBJECTIVES cont. <ul><li>Name several limitations of conventional file processing systems </li></ul><ul><li>Program-data dependence </li></ul><ul><li>Data redundancy </li></ul><ul><li>Poor data control </li></ul><ul><li>Inadequate data manipulation capabilities </li></ul><ul><li>Excessive programming effort </li></ul>
  11. 11. Introduction to DBMS - OBJECTIVES cont. <ul><li>Explain advantages of the database approach, compared to traditional file processing </li></ul><ul><li>Program-data independence </li></ul><ul><li>Eliminate problems with data redundancy </li></ul><ul><li>Flexibility </li></ul><ul><li>Security </li></ul><ul><li>Data Sharing and Availability </li></ul>
  12. 12. Traditional File Environment <ul><li>is a way of collecting and maintaining data in an organisation that leads to each functional area or division creating and maintaining its own data files and programs </li></ul><ul><ul><li>Payroll, Personnel, Benefit divisions maintaining their own data files and programs </li></ul></ul>
  13. 13. Conventional File Systems <ul><li>File Processing </li></ul><ul><ul><li>using Procedural Languages (e.g. COBOL) </li></ul></ul><ul><li>Processing Methods </li></ul><ul><ul><li>Sequential in Batch Mode to Interactive </li></ul></ul><ul><li>Main Problems </li></ul><ul><ul><li>Application programs dependent on the organisation of the file </li></ul></ul><ul><ul><li>Data Redundancy </li></ul></ul>
  14. 14. a) Program-data dependence is the close relationship between data stored in files and the software programs that update and maintain those files.
  15. 15. Program-data dependency ... Any change in data organisation or format requires a change in all the programs associated with those files. e.g. Payroll dept. use a data file containing information on employee names, addresses and salaries .
  16. 16. Program-data dependency ... <ul><li>Personnel dept. decided to use this file after adding no. of children to the data for each employee. </li></ul><ul><ul><li>A program to update the file, adding the required data on the number of children for each employee, would have to be written </li></ul></ul><ul><ul><li>Every program that accessed the data file would have to be rewritten so that each one could read the re-designed file. </li></ul></ul>
  17. 17. b) Data Redundancy <ul><li>is the presence of duplicate data in multiple data files. </li></ul><ul><li>Each department (Payroll, Personnel, Benefit) keep data on individual employees, in each of the department file. </li></ul><ul><li>employee name, department, salary scale in Payroll file; </li></ul><ul><li>employee name, address, gender, date of birth, department, date of appointment in Personnel file; </li></ul><ul><li>employee name, address, insurance scheme, pension plan in Benefit file. </li></ul>
  18. 18. e.g. Benefits application program <ul><li>Benefit file: </li></ul><ul><ul><li>Name, Address </li></ul></ul><ul><ul><li>Insurance, Pension plan </li></ul></ul><ul><li>Employee file: </li></ul><ul><ul><li>Name, Address, </li></ul></ul><ul><ul><li>NID number, Designation </li></ul></ul>e.g. Personnel application program <ul><li>Payroll file </li></ul><ul><ul><li>Name, Address </li></ul></ul><ul><ul><li>Hours worked, Pay rate </li></ul></ul>e.g. Payroll application program data files data files data files Application a Application i Application z
  19. 19. Data Redundancy cont. <ul><li>Problems: </li></ul><ul><li>extra effort required to input the duplicate data </li></ul><ul><li>additional computer storage needed to store the duplicate data </li></ul><ul><li>possibility for data inconsistencies </li></ul><ul><ul><li>name recorded with different spellings or format (surname first or initials or forenames first) </li></ul></ul><ul><ul><li>change of address recorded only by one of the dept. </li></ul></ul>
  20. 20. Database Approach DBMS data files <ul><li>e.g. </li></ul><ul><ul><li>Personnel application program </li></ul></ul><ul><ul><li>Payroll application program </li></ul></ul><ul><ul><li>Benefits application program </li></ul></ul><ul><li>e.g. Integrated </li></ul><ul><li>human resources database </li></ul><ul><li>Employees </li></ul><ul><ul><li>Name, Address </li></ul></ul><ul><ul><li>NID number, Designation </li></ul></ul><ul><li>Payroll </li></ul><ul><ul><li>Hours worked, Pay rate </li></ul></ul><ul><li>Benefit </li></ul><ul><ul><li>Insurance, Pension plan </li></ul></ul>Application i Application z Application a
  21. 21. Introduction to DBMS - OBJECTIVES cont. <ul><li>Explain the difference between conceptual, external and physical schemas and the reasons for a three-schema architecture for databases </li></ul>