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lecture-5.ppt lecture-5.ppt Presentation Transcript

  • WFM-6103: Hydrologic Information System (HIS) Akm Saiful Islam Lecture-5: Database Management System April-October, 2006 Institute of Water and Flood Management (IWFM) BUET Institute of Water and Flood Management (IWFM) Bangladesh University of Engineering and Technology (BUET) WFM 6103: hydrologic Information System © Dr. Akm Saiful Islam
  • Outline
    • Database Management System
      • Introduction to Databases
      • File System Vs. Databases
      • Advantages of using databases
      • Database Management System
    WFM 6103: hydrologic Information System © Dr. Akm Saiful Islam
  • Introduction to Databases
    • Information Systems process and manage data.
    • Data Management involves “Capturing”, “Retrieval,” and “Storage” of data.
    • Database Management Systems (DBMSs) are Computer systems that manage data in databases.
    • Today’s DBMSs are based on sophisticated software and powerful computer hardware.
    • Well known DBMS software includes ORACLE, Microsoft SQL Server, Sybase and MySQL(free download) among others.
    WFM 6103: hydrologic Information System © Dr. Akm Saiful Islam
  • Data Storage: Terminology
    • A collection of data entities is typically known as a file .
    • An individual data entity is typically known as a record .
    • Different attributes of a record are typically known as fields .
    • A key is a field or a set of fields that uniquely identifies a record.
    Fields Key Product Category + Product Type + Year File (table) WFM 6103: hydrologic Information System © Dr. Akm Saiful Islam Records
  • A Word on Keys
    • A Key maybe:
    • A field or set of fields that are used to identify the record.
    • A Primary key is a minimal set of fields that uniquely identifies the record.
    • A Foreign key is a field that is a primary key in another relation
    Primary Key Foreign Keys WFM 6103: hydrologic Information System © Dr. Akm Saiful Islam
  • File Organisation
    • Sequential Files
    • records are stored in a fixed sequence
    • records can only be read in that sequence, starting from the first record
    • records can only be added at the end of the file (append)
    • sequential files are not efficient
    • Indexed Files
    • Use an index to access records in a random fashion.
    • Records can be sorted according to an attribute or preference. (e.g Alphabetically, Ascending, Descending, etc.)
    • Indexed files are efficient, and faster to access.
    WFM 6103: hydrologic Information System © Dr. Akm Saiful Islam
  • The File Systems Approach
    • Redundant Data Storage.
    • One file is used in each application.
    • No data sharing.
    • Cross-application transfers are difficult to manage and achieve.
    • File Systems are rarely used for data processing anymore.
    WFM 6103: hydrologic Information System © Dr. Akm Saiful Islam General Ledger File Personnel File Production Planning File Inventory File Despatch File Order Entry File Invoicing File Payroll File
  • The Database Approach
    • Compactness. Data is stored in a single logical “place.”
    • Data can be shared and related between applications
    • Data transfer between applications is easier
    • Used for a wide range of applications.
    Database General Ledger Personnel Production Planning Inventory Despatch Order Entry Invoicing Payroll WFM 6103: hydrologic Information System © Dr. Akm Saiful Islam
  • Database Characteristics
    • • Amount
      • Database size depends on the number of records or files it contains.
    • Complexity
      • Database complexity depends on the number of relations between the files.
    • Volatility
      • A measure of the changes typically required in a given period of time.
    • Immediacy
      • A measure of how rapidly changes must be made to data.
    WFM 6103: hydrologic Information System © Dr. Akm Saiful Islam
  • Advantages of using a Database Approach
    • Flexible Data Access . DBMSs have various tools to manipulate, query, or report data, such as Structured Query Language (SQL), and Report Generators. Hence:
      • Selected data is easily retrieved
      • A DBMS can accommodate different data views for different users
    • Improved Data Integrity . Modern DBMSs consist of various tools and methods to:
      • ensure that data is correct, consistent, and current
      • verify data input and check whether data is ‘reasonable’.
    WFM 6103: hydrologic Information System © Dr. Akm Saiful Islam
  • Advantages of DBs (continued)
    • Improved Data Security . Tools such as password access, and encryption, ensure that data is not:
      • deliberately or accidentally damaged or changed
      • accessed without proper authorisation
    • Data Independence .
      • Problems arising from the interdependence of data and programs are kept to a minimum.
    • Reduced Data Redundancy.
      • Single version of the truth.
      • Efficient data storage.
      • Efficient time management of Hardware (CPU), programmer(s), analyst(s) and user(s).
      • Relational DBs use Normalisation to reduce data redundancy.
    WFM 6103: hydrologic Information System © Dr. Akm Saiful Islam
  • Advantages of DBs (continued)
    • Ability to Share and Relate Data .
      • Different user groups can use the same data.
      • Data in different (physical or logical) parts of the system can be related for a certain application.
    • Standardisation of Data .
      • In general data items have common names and storage format.
    • Increased Productivity .
      • The various tools reduce the complexity that is otherwise associated with DB maintenance when changes are required to the system. For example Law changes, Economy Changes, User Changes.
    WFM 6103: hydrologic Information System © Dr. Akm Saiful Islam
  • Costs of Database Approach
    • The implementation and use of DBMSs is normally associated with various costs. Such as:
      • Initial expenses involve planning costs, and consultancy fees.
      • Computer hardware costs.
      • Software costs.
      • Database Administrator costs, and staff training costs.
      • Conversion costs of an existing system.
      • Various operational costs.
    WFM 6103: hydrologic Information System © Dr. Akm Saiful Islam
  • DataBase Management System (DBMS)
    • A DBMS is a set of computer “programs” that control:
      • Database creation
      • Database maintenance
      • Database access
    • A DBMS typically includes:
      • a Data Definition Language or DDL
      • a Data Manipulation Language or DML
      • a Query Language. Quite often this is Structured Query Language (SQL) , or a derivative
      • a Report Generator
    WFM 6103: hydrologic Information System © Dr. Akm Saiful Islam
  • The DBMS Manages the Interaction Between the End User and the Database Bangladesh University of Engineering and Technology © Dr. Akm Saiful Islam
  • References
    • Alex Berson, and Stephen J. Smith, Data Warehousing Data Mining, and OLAP, McGraw Hill, 1997. Chapters 1,13(13.1-13.4 inc.). ISBN 0-07-006272-2
    • C. J. Date, An Introduction to Database Systems, 3rd Ed. (or later), Addison-Wesley, 1981. Chapter 1.
    • J. A. Senn, Analysis and Design of Information Systems, 2nd Ed. (or later), McGraw-Hill 1989. Chapter 12 (“Design of DB Interactions”). ISBN 0-07-100606-0
    • E. Turban J. Aronson, Decision Support Systems and Intelligent Systems, 5th Ed., Prentice-Hall, 1998. Chapter 4. ISBN 0-13-791675.
    WFM 6103: hydrologic Information System © Dr. Akm Saiful Islam