Topic 8: Database 1

Topic 8: Database 1

1. Data Type

   • Number (integer)
     • a whole number (that can be positive or negative)
       • For example, 43
   • Number (real)
     • any number (that can be whole numbers and fractions)
       • For example, 435.256
   • Text/String
     • letters, numbers or other characters such as punctuation marks
       • For example, John Smith
   • Date/Time
     • any time or date - the way in which it is displayed depends on the formatting
       • For example, 04/10/12 12:15:45
   • Currency
     • money (£), including foreign currencies ($, €)
       • For example, £13.55
   • Boolean
     • two opposing states
       • For example, yes or no, true or false
   • Lists
     • a list of values, sometimes called 'drop-down' list; only data from this list can be selected.
       • For example, Red Green Blue

2. Files/Tables

   • File
     • (table) - collection of related fields
       • the table of records of pupils in a school
   • Record
     • consists of a collection of related fields
       • in a school, all the data related to that pupil and no one else
   • Field
     • a single item of data within a record
       • field name : field type price : currency
   • Key Field
     • uniquely identifies each record (ID no., bar code, membership no.)
       • Pupil ID

3. Validation

   • Data must be sensible & reasonable
   • Validation methods
     • Length check
       • length of input checked for no. of characters
     • Presence check
       • ensures data is entered into that field
     • Range check
       • data must be entered within a specific range
     • Type check
       • ensures data is the correct data type
     • Format check
       • ensures data is the correct format (e.g. date: dd/mm/yyyy)
     • Lookup list
       • if possibilities of data is limited, this checks that the data entered is within the list of answers allowed

4. Calculated fields

   • a field such as 'age' would be calculated because it constantly changes every day
   • it calculates the age by subtracting the d.o.b from the date of the report