3. Types of Validation

Some of the types of Validation that you could set up are:

Validation Techniques
Validation	Example
Type Check Sometimes you only want data of a certain type entered into a field. For example, in a clothes shop, dress sizes may range from 8 to 18. A number datatype would be a suitable choice for this data. By setting the datatype as number, only numbers could be entered and you would prevent anyone trying to enter ‘ten’ or ‘ten and a half’. Some data types can perform an extra type check. For example, a date data type will ensure that a date you have entered can actually exist e.g. it would not allow you to enter the date 31/02/07.	2, 3, 4 14/05/07
Range Check A shop may only sell items between the price of £10.00 and £50.00. To stop mistakes being made, a range check can be set up to stop £500.00 being entered by accident. Another example might be that a social club may not want people below the age of 18 to be able to join. Notice the use of maths symbols: > 'greater than' < 'less than' = equals	>=10 AND <=50 >=18
Presence check There might be an important piece of data that you want to make sure is always stored. For example, a school will always want to know an emergency contact number, a video rental store might always want to know a customer's address, a wedding dress shop might always want a record of the brides wedding date. A presence check makes sure that a critcal field cannot be left blank, it must be filled in.	School database: Emergency contact number DVLA database: Date test passed Electoral database: Date of birth Vet's database: Type of pet
Picture or format check Some things are always entered in the same format. Think about postcode, it always has a letter, letter, number, number, number, letter and letter e.g. CV43 9PB. There may be the odd occasion where it differs slightly e.g. a Birmingham postcode B19 8WR, but the letters and numbers are still in the same order. A picture or format check can be set up to make sure that you can only put letters where letters should be and numbers where numbers should be.	Postcode: CV43 9PB Telephone number (01926) 615432
Check Digit This is used when you want to be sure that a range of numbers has been entered correctly for example a barcode or an ISBN number: ISBN 1 84146 201 2 The check digit is the final number in the sequence, so in this example it is the final ‘2’. The computer will perform a complex calculation on all of the numbers and then compare the answer to the check digit. If both match, it means the data was entered correctly.	ISBN 1 84146 201 2

Challenge see if you can find out one extra fact on this topic that we haven't already told you

Click on this link: Database Validation