Miss allsop Databases

• a range check ensures that data is between an upper and lower acceptable value, within a certain range

  They are useful for dates, not just numbers

  eg: we could check that a date of birth puts a customer within an acceptable age range.
• type check ensures that data entered is of an unexpected type eg: a number or date

  the data needs to be the right type in order to allow processing later on
• length check ensures that the number of characters meets expectations eg: 8 character password.
• a format check ensures the data follows a set pattern (using an input mask)

  eg: UK postcodes follow a particular sequence of letters and numbers, helps make sure the postcode is realistic
• presence check ensure the user has at least entered something into the fields stopping them form accidently leaving it empty
• presence check example:

  • go to design view
  • in validation rule type in ‘ is not null’

  this tells the system to do the actual check

  • in validation message/text - write a message that is appropriate that pops up if the user leaves blank

  eg: ‘silly human you must enter a value here’
• format and length check:

  • go to design view
  • next to field size enter 11
  • Uk phone numbers are typically
  • default is 255- you change it to whichever is suitable to the field name u have chosen
  • it wont let you type anymore than the chosen number