Databases

Databases

1. Types of Data

   • Number (integer)
     • A whole number (positive or negative but no fractions)
     • 43
   • Number (Real)
     • Any number including whole numbers and fractions
     • E.G. 432.51
   • Text/string
     • Letters, numbers or other characters such as punctuation marks
     • John Smith
   • Date/Time
     • Any time or date. The way the time or date is displayed depends on how it is formatted
     • E.G. 04/10/06 12:23:09
   • Currency
     • Money (including foreign currencies such as $ or euros
     • £12.50
   • Boolean
     • The data can have only two possible outcomes such as 'yes' or 'no', 'true' or 'false', 'male' or 'female'
   • Lists
     • The data is in the form of the list
   • Picture
     • Image data from a digital camera, mobile phone, the internet, a clip-art library or scanned drawing
   • Sound
     • A beep from a bar code reader or a popular song
   • Video
     • A video introduction to a computer game or a downloaded film/tv

2. Database validation

   • Range check
     • Ensures that the data entered is within a sensible range
   • Type check
     • Ensures that the data is of the correct data type
   • Length check
     • Ensures that the length of the input for the number of characters is used
   • Lookup list
     • Checks that the entered against a limited number of possible enteries
   • Picture/Format check
     • Ensures that the data being entered has a particular pattern, such as a post code.
   • Input mask
     • Is used to force the data to conform to a rule. The computer checks to see that the entry conforms to that pattern.
   • Presence check
     • Ensures that certain data is present

3. Key information

   • An organised collection of related data
   • It is possible to edit, add, manage and retrieve data
   • The structure of a database allows data to be found and used quickly
   • Data is stored in the computer in binary form as series of 0s and 1s
   • In order to process the data the computer needs to know the data type

4. Key words

   • Key Field
   • Validation
   • Reports
   • Field
   • Records
   • Files
   • Query

5. Wildcards

   • *
     • Any number of characters
   • ?
     • Any character
   • []
     • Any character within a range of characters
   • [-]
     • Any character in the brackets
   • !
     • Any character not in the brakets

6. Operators

   • =
     • Equals
   • <
     • Less than
   • >
     • Greater than
   • <>
     • Not equal to
   • AND
     • Data is only listed where both conditions are true
   • OR
     • Data is only listed where either or both conditions are true
   • LIKE
     • Where a perfect match is not needed