1. Validation and Verification
Y11 Databases

2. Validation and Verification…
Once you have a set of data, you need to enter it into your database system You need to devise methods to reduce the number of errors that may occur when entering data GIGO (Garbage In Garbage Out) Two of the techniques used are Validation and Verification…

3. Validation
Validation is performed by the computer at the point when you enter data
You create a set of rules
Validation aims to make sure that data is sensible, reasonable, complete and within acceptable boundaries
Validation does not check that the data is correct!
For example, if you type in 07/08/07 as a date of birth when it should have been 08/07/08 – validation will not pick this up!

4. Range Check
A range check is commonly used when you are working with data which consists of numbers, currency or dates/times
A range check allows you to set suitable boundaries:

5. Type Check Setting the correct data type for the field
setting a field as NUMBER so that only “11” can be entered rather than “Eleven”

6. Check Digit
Check digits are used to make sure a range of numbers has been entered correctly
For example, barcodes and ISBN numbers
ISBN
The “2” is the check digit
The computer will perform a complex calculation based on the numbers provided and then compare the answer to the check digit

7. Length Check

8. Lookup

9. Picture/Format Check

10. Presence Check

11. Common Errors

12. Verification

13. Verification Methods