S3+ISDD+Validation

Validation
Validation is the process of ensuring that data entered into a database meets a certain rule or rules. There are different types of validation checks which can be performed on a database:


 * Presence check ** - does the field have to have a value entered?


 * Restricted choice check ** - the value entered has to be of a certain value (e.g. Mr / Mrs / Miss / Ms)


 * Range check ** - the value entered has to fall within a certain range (e.g. 0-100)

** Questions **
1. What is meant by the validation of a database field?

2. Describe what is meant by a presence check

3. Describe what is meant by a range check

4. Describe what is meant by a restricted choice check

5. A car showroom keeps a database of all the cars which have been sold. An extract from the database is shown below:



(a) Suggest a suitable validation check for the Date Sold field

(b) Suggest one field which should have a presence check

(c) Suggest one field which does not need a presence check

6. A school office keeps a database of all of the pupils at the school, as shown below:

State 2 validation checks which might be used on the Sex field. Explain your choice for each.

7. Duncastle United Football Club runs a membership scheme for fans, as shown below.



When the club secretary tries to enter this record, they get an error message. Explain why the error message has appeared and what the secretary should do to resolve the problem.