Loading…

Flash Player 9 (or above) is needed to view presentations.
We have detected that you do not have it on your computer. To install it, go here.

Like this presentation? Why not share!

Like this? Share it with your network

Share
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Be the first to comment
    Be the first to like this
No Downloads

Views

Total Views
1,303
On Slideshare
1,301
From Embeds
2
Number of Embeds
1

Actions

Shares
Downloads
68
Comments
0
Likes
0

Embeds 2

http://itgscs2011.wikispaces.com 2

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
    No notes for slide

Transcript

  • 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
    processing
    Output
    Stages of Processing Data
    data
    information
  • What is a Database?
    An organised collection of data items that are related to a particular topic, purpose or activity
    Examples:
    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
    file
    fields
    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
    record
    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
    records
    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)
    Image/Picture
  • 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
    Tables/files
    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