Databases

Databases

1. Data types

2. Key words

   • Report
   • Form
   • Validation
   • Query
   • Validation rule
   • database
   • Update
   • Sort
   • Ascending
   • descending
   • Security
   • Softwware
   • operator
   • Wildcard
   • Password
   • Editing
   • Primary Key
   • Shortcuts
   • Accuracy
   • Access
   • Input
   • Field
   • Record
   • Back up

3. Validation

   • Data entered into a database must be sensible or we get GIGO.
   • Validation methods can only ensure reasonable and sensible data is input into a system, but there is no certainty that the data is correct.
   • Validation rules are needed for some fields. As data is entered it is checked to see that it obeys the rules; any data that does not obey the rules is not accepted.
   • You can set validation text- the text that appears if the data is not acceptable
   • Range check- the data entered must be in a sensible range- e.g. if a test is out of 100 marks then only marks in the range of 0-100 are accepted
   • Type check- This ensures that the data is of the correct type-e.g. if the number of rooms in a house is being recorded the only an integer (whole number) can be entered
   • Format/Picture Check- If the data entered has a particular pattern e.g. a postcode or car reg then an input mask can be used to force the data to conform to the rule- e.g. Input mask for a postcode would be LLN NLL e.g. ME1 3BY Where a Letter L is a letter and N is a number
   • Length check- The length of input is checked for the number of character used
   • Presence check: Some data of some form has to be entered: If you were ordering goods from the internet you would have to give them your address and the item you were ordering. An error would occur if this data was not present and would not allow the processing of the order to continue.
   • Lookup list: if the data entered consists of a limited number of possible entries then the computer can compare the entry list with a list of allowed answers