Lesson Objectives:
- Explain what verification is and why it is used.
- Create a database that is fully validated.
- Discuss what validation is and how it helps to reduce human error.
Validation and verification are two ways to check that the data entered into a computer is correct. Data entered incorrectly is of little use.
Validation
Validation is an automatic computer check to ensure that the data entered is sensible and reasonable. It does not check the accuracy of data. For example, a secondary school student is likely to be aged between 11 and 16. The computer can be programmed only to accept numbers between 11 and 16. This is a range check.
However, this does not guarantee that the number typed in is correct. For example, a student’s age might be 14, but if 11 is entered it will be valid but incorrect.
Types of validation
There are a number of validation types that can be used to check the data that is being entered.
| Validation type | How it works | Example usage |
|---|---|---|
| Check digit | The last one or two digits are correct | Bar code readers in supermarkets use check digits |
| Format check | Checks the data is in the right format | A National Insurance number is in the form LL 99 99 L where L is any letter and 9 is any number |
| Length check | Checks the data isn’t too short or too long | A password which needs to be six letters long |
| Lookup table | Looks up acceptable values in a table | There are only seven possible days of the week |
| Presence check | Checks that data has been entered into a field | In most databases a key field cannot be left blank |
| Range check | Checks if a value falls within the specified range | Number of hours worked must be less than 50 and more than 0 |
| Spell check | Looks up words in a dictionary | When word processing |