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Database concepts presentation version 2010 revised



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  • 1. Database Concepts
    Created by M Nodalo, Port Moresby International School for Year 11 Information Technology (T) - ACT/BSSS, revised 2010
  • 2. Objective
    So that students will be able –
    to discuss the basic database concepts and terminologies – data, information, field, record, key field, computed fields, field length, data types, etc.
    To discuss the concept of relational database and flat-file database
    To discuss the concept of SQL (structured query language)
  • 3. Data Vs. Information
    Data – raw fact or figures
    Example : Max Freeman 55,000 25
    Information – data that have been
    processed to be meaningful to the user
    Example: K55,000 x .25 = K13,750
    Max Freeman is a salesman who earned K55,000 sales for this month and therefore, receives 25% commission which is K13,750.
  • 4. Input
    Stages of Processing Data
  • What is a Database?
    An organised collection of data items that are related to a particular topic, purpose or activity
    a telephone directory, an address book, student class list
  • 10. Databases can be stored
    Manually (in a filing cabinet with index cards, 3-ring binders, file folders)
    Electronically using a computer system (with suitable database software)
  • 11. Manual databases - concerns
    Data duplication – same data on each file
    Effects of data duplication:
    More space is taken up by the files
    More work is needed to retrieve the information
  • 12. Advantages of Computerised Databases over Paper files
    Easier to store large volume of information
    Easier to retrieve information quickly /flexibly
    Speed of information processing
    Versatility/flexibility in organising & reorganising information
    Easier to display, print & distribute information in a variety of ways
    Validation checks may be made on the data (done by a computer program)
  • 13. Disadvantages of Computerised database over paper files
    Unable to access data when there’s a computer breakdown
    Ease of copying computer files; passwords needed for extra protection
    Extra cost & time to train people to use the database
  • 14. Planning a Database
    Define the purpose of the database
    Determine the type of output reports
    List all the data items (determines the fields)
  • 15. Employee file
    Name: Venus Jackson
    Age: 27
    Home Address: Gere-gere Ave., Boroko, NCD
    Gender: Female
    Job Position: Accounts Clerk
    Pay Rate/FN: 750.00
    Years in Service: 5
    Database Structure
    Table – a collection of related records
    Record – a collection of data about a person or thing made up of one or more fields
    Field – a single piece of data or information common to all records
  • 16. Example of a DatabaseTelephone Directory
    File/table name
    Field name
    Telephone Directory
    Name Address Phone Number
    Aldo,Mark East Boroko 323-2932
    Amani,James Hohola 325-9022
    Artona,Kathy Port Moresby 323-4325
    Field data
  • 17. Two parts of a field:
    Field name – words that represent each field data or information, e.g.
    name, address, phone number, etc.
    2. Field data – the actual data or
    information item stored in a field,
    e.g. Mary Jones, Boroko, 325-3423
  • 18. Designing a Record
    Field names
    Type of data (text, numeric, date, boolean, image)
    Field length or size – the total number of characters allowed for a particular field
    Field description
  • 19. Field length/size
    Should be designed to cope with the largest entry possible without reserving unnecessary disk space
    Too long field sizes –
    - will take up more space on the storage media (floppy/hard disk/CDs/flash drives)
    - takes longer to process
  • 20. Types of Data
    Numeric – contains only numbers
    Character text – numbers, letters & other symbols can be entered
    Date – date is entered as 01/09/04
    Logical (Boolean) – allows Y/N (yes/no) or T/F (true/false)
  • 21. Key Field
    A field that may be used to search a file
    It makes a record unique from other records in the file
    e.g. student ID number, Book ID number,
    employee ID, customer code
  • 22. Computed field
    Contain formulas similar to spreadsheet formula
    They display values calculated from values in other numeric fields
    Example: Net Pay may contain formula which calculates an employee’s net pay using Gross Pay and Tax fields
  • 23. Sample database: Student file
  • 24. Features of Computerised Databases
    Create fields
    Add and alter records
    Search for specific records
    Sort records
    Print reports
  • 25. What is DBMS?
    DBMS – Database Management System
    A computer program that allows you to set up a database on computer.
    • build a database
    • 26. add new data, delete or edit existing data
    • 27. search and extract specific data based on certain criteria (query)
    • 28. change/alter the structure of the data file
    • 29. sort and reorganise data
    • 30. display data on screen / print reports
    • 31. security of allowing certain people to access files
  • What is MS Access?
    An example of a DBMS which was developed by Microsoft Corporation.
  • 32. Database Terms in Access
    Fields (columns)
    Records (rows)
    table – refers to a file in Access
  • 33. Database Queries
    • Issues
    • 34. the incompatibility of database languages
    • 35. created difficulty for people using different applications to access the same database
    • 36. E.F. Codd (IBM) – proposed the standardized structured English Query Language or what evolved as the SQL
  • Structured Query Language (SQL)
    Not a database management system
    Not a full-featured programming language like Java or C+.
    It is a sublanguage tailored for the database environment
    SQL statements – embedded inside computer programs such as COBOL, C or other programming languages
    SQL statements – understood by MS Acccess, MS SQL Server, DB2, Oracle, Sybase & other database programs
  • 37. Structured Query Language (SQL)
    Combines database concepts of
    Records (rows)
    Fields (columns)
    Mathematical concept of set
    See example on pages 234-235 (Chapter 7 Database Applications and Privacy Implications, Tomorrow’s Technology and You) – 7.1 The Language of Database Queries
  • 38. Structured Query Language (SQL)
    Basic SQL statements – filters the records of a database to be able to extract only those records that meet specific criteria
    SQL statement format:
    SELECT (specify fields to extract)
    FROM (specify source – file name)
    WHERE (specify criteria or condition using appropriate comparison operators such as AND, OR, NOT, =, >, <, <>, >=, <=)
  • 39. Types of Databases
    • Flat file database – uses only one file at a time
    Example: MS Excel – spreadsheet list
    • Relational database – consists of several files in which data can be accessed simultaneously
    Example: MS Access
  • 40. Relational Database
    Relational database links some tables with certain data common with other tables.
  • 41. Sources
    • Chapter 7 – Database Applications & Privacy Implications, Tomorrow’s Technology and You (8th ed) by G. Beekman & M. Quinn