Validation is the process by which computer makes sure that the data being entered is correct.

There are methods of validation. They are:

Methods of validation
Type checking
Make sure that the data entered is of correct type
Presence check
Make sure an important data is not missed out
Range check
Make sure that the data lies in an acceptable range of values
Length check
Make sure that the data contain required number of characters in it.
Check digit
Check digit is the last digit of barcodes and ISBN numbers. While reading these codes computer do some calculation with the of the digits and compares with the check digit to validate the barcode or ISBN number.
Batch total
It is the total of anumeric field, such as Amount, Quantity, Price, Fees, etc.
Hash total
Hash total is also total of a numerical field but it is a meanngless total, like total of phone number field, employee_id, etc.

It is the process in which a person goes through the database to check for any errors in the data, after the data has been entered into the system.

Methods used for verification are:

1. Visual check/Visual verification:
After the data has been entered a person compares the original data with the data in the computer (either on the screen or using a print-out). If mistakes are spotted they can be corrected by the person.

Advantage: Visual check is quick and simple

Disadvantage: But doesn’t catch every mistake.

2. Double-Entry
The data is entered into the computer twice (preferably by two different people). The computer compares the two sets of data to see if they match. If not it generates an error and a person will need to correct the mistake.

Disadvantage: Double-entry takes more time and effort

Advantage: But it catches almost every mistake..