Database T8

Database T8

1. Data Types

   • Number (integer)
     • 43
     • Whole Number (positive and negative) but no fractions
   • Number (real)
     • 435.256
     • Any number, including whole numbers and fractions
   • Text/String
     • John Smith
     • letters, numbers or other characters such as punctuation marks
   • Date/Time
     • 04/12/14 12:15:45
     • Any date or time; the way the time or date is displayed depends on how it is formed
   • Currency
     • £13.33
     • Money
   • Boolean
     • Yes
     • Two opposing states e.g. true or false, yes or no
   • Lists
     • Red Green Blue
     • A list of values sometimes called a "drop-down"
   • Picture
     • Image data, from a digital camera or mobile phone
   • Sound
     • A sound or music clip
     • A beep from a barcode reader or popular song
   • Video
     • A moving picture
     • A video introduction to a computer game or TV/film show

2. Files, Records and Fields

   • Field
     • A single item of data within the record
     • Example
       • Surname
       • DOB
       • Selling Price
   • Records
     • consists of a collection of related fields
     • Example
       • Pupils record in a school database
   • Files
     • (Known as a table in Microsoft Access)
     • collection of related fields
     • Example
       • the table of records of all pupils in a school

3. Key Fields

   • a key field uniquely identifies each record
   • No two records have the same data in there key field
   • PupilID

4. Validation

   • must be sensible other wise we get GIGO
   • Ensures data is reasonable and sensible. doesn't have to be correct
   • Are needed for some fields
   • The data entered must be acceptable other wise you will get an error message

5. Validation methods

   • Range check
     • the data entered must be of an acceptable range
   • Type Check
     • ensures the data entered is of the correct type e.g. text
   • Format/Picture text
     • the data entered has a particular pattern e.g. postcode or barcode
   • Length Check
     • the length of the input is checked for the number of characters used
   • Presence Check
     • some data has been entered e.g. your address when ordering things online
   • Lookup List
     • data entered consists of a limited number of possible entries the computer can compare allowed answers

6. Reports

   • a report is a printed document that contains data from a database
   • organised and analysed in a certain way

7. Forms

   • Used to make data more attractive and secure rather than it being entered into raw tables

8. Calculated fields

   • not all data needs to go in a database e.g. age
   • your age changes day by day so if you want to include it you put it in a calculated field

9. Uses of databases

   • add, change or delete records
   • search for a particular record
   • sort the records into a given order
   • print reports

10. Updating Records

    • records don't stay the same forever
    • e.g. someone may get married
    • adding a new record
    • edit existing records
    • deleting an old record

11. Searching for data

    • you use a query
    • 'query the database'
    • specifies what you are searching for in a record
    • Simple query search (looks for data in one field)
    • Complex query search (looks at data with multiple critera

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