Databases

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Databases

  1. 1. Introduction to Databases
  2. 2. Databases <ul><li>A database is a collection of related pieces of information </li></ul><ul><li>A database can be computerised or non-computerised (manual - such as filing system, phone book etc.) </li></ul>
  3. 3. Advantages of Computerised Databases <ul><li>speed of information retrieval </li></ul><ul><li>storage capabilities </li></ul><ul><li>easy to update and delete </li></ul><ul><li>ease of access </li></ul><ul><li>multiple access </li></ul><ul><li>security </li></ul>
  4. 4. Disadvantages of Computerised Databases <ul><li>privacy and ethical issues </li></ul><ul><li>security risks </li></ul><ul><li>training of staff </li></ul><ul><li>initial expense (equipment, software) </li></ul><ul><li>software upgrades </li></ul>
  5. 5. Terminology <ul><li>A database or a table within a database is made of RECORDS </li></ul><ul><li>RECORDS contain information about a single item in the database/table. </li></ul><ul><li>Each record contains FIELDS . </li></ul><ul><li>A FIELD is a category of data that has been broken down into its simplest form. </li></ul><ul><ul><li>Firstname, surname, street, suburb </li></ul></ul>
  6. 6. Terminology <ul><li>In a database or table each ROW represents a record </li></ul>ID CDTitle Units In Stock Unit Price 1 Joe Cocker Essentials 3 $28.00 2 The Beatles 4 $35.00 3 Aussie Country Hits 2 $19.95
  7. 7. Terminology <ul><li>each COLUMN represents a field. </li></ul>. ID CDTitle Units In Stock Unit Price 1 Joe Cocker Essentials 3 $28.00 2 The Beatles 4 $35.00 3 Aussie Country Hits 2 $19.95
  8. 8. Terminology <ul><li>Every record in the same table has the same fields. </li></ul><ul><li>Databases are designed so that each data item is stored only once </li></ul>
  9. 9. Terminology <ul><li>The method of retrieving information from the database is known as QUERYING the database. </li></ul><ul><li>A query allows you to display a set of records which meet certain criteria </li></ul><ul><ul><li>students in year 9 </li></ul></ul><ul><ul><li>people with postcode 6192 etc. </li></ul></ul>
  10. 10. Terminology <ul><li>Information taken from a database and designed for hardcopy (printout) is referred to as a REPORT . </li></ul><ul><li>Reports can be generated from tables or queries. </li></ul><ul><li>Reports can be formatted in many different styles depending on the target audience. </li></ul>
  11. 11. Terminology <ul><li>Other database operations include: </li></ul><ul><li>SEARCHING </li></ul><ul><ul><li>locate the first record to contain some specific criteria </li></ul></ul><ul><li>SORTING </li></ul><ul><ul><li>sorting the database by a nominated field </li></ul></ul>
  12. 12. Terminology <ul><li>Some database applications also provide a user friendly interface called a FORM . </li></ul><ul><li>Forms are used to display data from a table or query in an easy to read format. </li></ul>
  13. 13. Planning a Database <ul><li>Careful planning of a database before it is created will prove to be a useful exercise. </li></ul><ul><li>Step 1 </li></ul><ul><li>Determine what data should be stored in each record. </li></ul><ul><li>Generate a list and eliminate information that is not directly related to the overall purpose of the database. </li></ul>
  14. 14. Planning a Database <ul><li>Step 2 </li></ul><ul><li>What operations are to be performed on the database? </li></ul><ul><li>Do these operations require any missing information from the list? </li></ul><ul><li>Will there be any need to reduce the list further? </li></ul><ul><li>Adjust the list from step 1 </li></ul>
  15. 15. Planning a Database <ul><li>Step 3 </li></ul><ul><li>Create a list of fields and field names from step 2 </li></ul><ul><li>Create a description of the data and their types (text, number, YES/NO etc) </li></ul><ul><li>Design a simple form for a single record on paper </li></ul>
  16. 16. Planning a Database <ul><li>Step 4 </li></ul><ul><li>Create a new database/table using your software with the planned fields. </li></ul><ul><li>Enter the data into database </li></ul>

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