Chapter 1 ® Introduction to Database Management


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Chapter 1 ® Introduction to Database Management

  1. 1. Chapter 1 <ul><li>Introduction to Database Management </li></ul>Database Management
  2. 2. Objectives <ul><li>Provide a general introduction to the field of database management </li></ul><ul><li>Introduce basic terminology </li></ul><ul><li>Describe the advantages and disadvantages of database processing </li></ul><ul><li>Provide a brief history of database management </li></ul><ul><li>Describe the hierarchical and network database models </li></ul>
  3. 3. Introduction <ul><li>Chapter uses the example of Henry, the owner of four bookstores </li></ul><ul><li>Current file system is difficult and costly to use </li></ul><ul><li>Interested in different categories of data, called entities , including books, authors, publishers, and branches, and the relationships between these entities </li></ul>
  4. 4. Henry’s Basic Data <ul><li>File - an organized collection of data about a single entity </li></ul><ul><li>Record - pertains to a specific person, place, thing, or event </li></ul><ul><li>Fields - contain certain facts about that specific person, place, thing, or event </li></ul>
  5. 5. Figure 1.1 Branch File
  6. 6. Figure 1.2 Publisher and Author Files
  7. 7. Figure 1.3 Book File
  8. 8. Figure 1.4 Book-Author and Book-Branch Files
  9. 9. Using a Database Management System (DBMS) <ul><li>A DBMS is a program or collection of programs whose function is to manage a database on behalf of the people who use it. </li></ul><ul><li>Database design is the determination of the structure of the database. </li></ul>
  10. 10. Figure 1.5 Branch Form
  11. 11. Figure 1.6 Book Form
  12. 12. Figure 1.7 Book Report
  13. 13. Figure 1.8 Main Switchboard
  14. 14. Figure 1.9 Maintain Data Switchboard
  15. 15. Entities, Attributes, and Relationships <ul><li>Entity – a person, place, thing, or event </li></ul><ul><li>Attribute – a property of an entity </li></ul><ul><ul><li>For the entity “Person,” attributes could include eye color and height </li></ul></ul><ul><li>Relationship – an association between entities </li></ul><ul><ul><li>Publishers are related to the books they publish, and a book is related to its publisher </li></ul></ul>
  16. 16. Figure 1.10 Entities and Attributes
  17. 17. Figure 1.11 One-to-Many Relationship
  18. 18. Files and Databases <ul><li>Data file – stores information on a single entity and the attributes of that entity </li></ul><ul><li>Database – a structure that can store information about multiple types of entities, the attributes of these entities, and the relationships among the entities </li></ul>
  19. 19. Database Management System (DBMS) <ul><li>DBMS programs manipulate databases either for the user, or a program the user is executing </li></ul><ul><li>Mainframe DBMSs have been used since the 1960s </li></ul><ul><li>Since the mid-1980s, DBMSs on PCs possess many of the features of their mainframe counterparts </li></ul>
  20. 20. Figure 1.12 Using Database Management Systems
  21. 21. Database Processing <ul><li>Database processing – the data to be processed are stored in a database and the data in the database are being manipulated by the DBMS </li></ul><ul><li>Nondatabase approach </li></ul><ul><ul><li>Duplication of data </li></ul></ul><ul><ul><li>Extremely difficult to fulfill requirements that involve data from more than one system </li></ul></ul>
  22. 22. Figure 1.13 Nondatabase Approach
  23. 23. Database Processing <ul><li>Database approach </li></ul><ul><ul><li>Common database managed by a DBMS </li></ul></ul><ul><ul><li>Each entity appears only once in the system, reducing the duplication of data </li></ul></ul><ul><ul><li>With all data being in a single database, it is possible to list all information concerning the entities </li></ul></ul>
  24. 24. Figure 1.14 Database Approach
  25. 25. Figure 1.15 Advantages of Database Processing
  26. 26. Advantages of Database Processing <ul><li>Getting more information from the same amount of data </li></ul><ul><ul><li>When all the data for various systems are stored in a single database, the information becomes available, as well as the process of retrieving the information can be quick and easy </li></ul></ul>
  27. 27. Advantages of Database Processing <ul><li>Sharing of data </li></ul><ul><ul><li>Several users can have access to the same piece of data </li></ul></ul><ul><li>Balancing conflicting requirements </li></ul><ul><ul><li>A person or group, often called Database Administration/Administrator (DBA) can structure the database in such a way that it benefits the entire organization, not just a single group </li></ul></ul>
  28. 28. Advantages of Database Processing <ul><li>Controlling redundancy </li></ul><ul><ul><li>Not only saves space, but makes the updating process easier </li></ul></ul><ul><li>Consistency </li></ul><ul><ul><li>Consistency is a direct result of redundancy, so by reducing redundancy, there is much less potential for this sort of inconsistency with the database approach </li></ul></ul>
  29. 29. Advantages of Database Processing <ul><li>Integrity </li></ul><ul><ul><li>An integrity constraint is a rule that must be followed by data in the database </li></ul></ul><ul><ul><ul><li>Example: Not allowing a person’s age to be lower than zero </li></ul></ul></ul><ul><li>Security </li></ul><ul><ul><li>The prevention of access to the database by unauthorized users </li></ul></ul>
  30. 30. Advantages of Database Processing <ul><li>Increasing productivity </li></ul><ul><ul><li>A good DBMS comes with many features that allow users to gain access to data without having to do any programming at all </li></ul></ul><ul><li>Data independence </li></ul><ul><ul><li>A property that allows the structure of a database to be changed without the programs that access the database having to change </li></ul></ul>
  31. 31. Figure 1.16 Disadvantages of Database Processing
  32. 32. Disadvantages of Database Processing <ul><li>DBMS size </li></ul><ul><ul><li>DBMSs are large programs that occupy a large amount of disk space as well as internal memory </li></ul></ul><ul><li>DBMS complexity </li></ul><ul><ul><li>The complexity and breadth of the functions provided by a DBMS make it a complex product to use </li></ul></ul>
  33. 33. Disadvantages of Database Processing <ul><li>Greater impact of a failure </li></ul><ul><ul><li>A failure on the part of any one user that damages the database in some way may affect all the other users on the system </li></ul></ul><ul><li>More difficult recovery </li></ul><ul><ul><li>If the database is being updated by a large number of users, all updates must be redone since the time of its restoration </li></ul></ul>
  34. 34. History of Database Management <ul><li>IBM developed the Generalized Update Access Method (GUAM) in 1964 for North American Rockwell, the prime contractor for the APOLLO project </li></ul><ul><li>GUAM was made available for the general public under the name Data Language/I (DL/I) in 1966 </li></ul>
  35. 35. History of Database Management <ul><li>DL/I became the data management component for the Information Management System (IMS), which was the dominant DBMS for many years </li></ul><ul><li>In the mid-1960s, General Electric developed Integrated Data Store (I-D-S) </li></ul>
  36. 36. History of Database Management <ul><li>The COnference on DAta SYstems Languages (CODASYL) tackled the problem of providing standards for DBMSs in the late 1960s </li></ul><ul><li>In 1971, the CODASYL standards were presented to the American National Standards Institute (ANSI) </li></ul>
  37. 37. History of Database Management <ul><li>Throughout the 1970s, the relational model was the subject of intense research </li></ul><ul><li>The 1980s is when the first commercial relational DBMSs appeared </li></ul><ul><li>The 1980s saw the development of object-oriented database management systems (OODBMSs) </li></ul>
  38. 38. Hierarchical and Network Databases <ul><li>Four types of data models </li></ul><ul><ul><li>Network </li></ul></ul><ul><ul><li>Hierarchical </li></ul></ul><ul><ul><li>Relational </li></ul></ul><ul><ul><li>Object-oriented </li></ul></ul>
  39. 39. Network Model <ul><li>Perceived by the user as a collection of record types and relationships between these record types </li></ul><ul><li>I-D-S and other CODASYL systems are examples of DBMSs that conform to the network data model </li></ul>
  40. 40. Figure 1.17 Network Database Structure
  41. 41. Hierarchical Model <ul><li>Perceived by the user as a collection of hierarchies, or trees </li></ul><ul><li>More restrictive structure than a network model </li></ul><ul><li>GUAM, DL/I, and IMS are examples of DBMSs that conform to the hierarchical model </li></ul>
  42. 42. Figure 1.18 Hierarchical Database Structure