Data Validation

All data entered into a system is validated. Data validation is performed by a computer program. There are a variety of validation methods used on data to ensure accurate entry of data. Let’s look at some of the validation methods used:

1. Length Checks

In this validation technique, data entered is checked to make sure it is a particular length, for example 4 characters, if it’s greater or less than 4 characters it is detected as an error.

1. Range Checks

Here data is checked to lie within a specified range as in if integers (numerical values) were entered a range of 10 – 1000 may be specified in which case all entered data must be in between 10 & 1000.

1. Presence Checks

This is a simple check performed to check if data has been entered into a field, it makes sure required fields are not left blank.

1. Character Checks (or Character Type Check)

This checks if data entered is a particular character type, for example it may check that a ‘name’ field has only letters.

1. Check Digit

A check digit is a single digit generated from a complete number, for example an ISBN contains a check digit, the last digit of the ISBN is a check digit. It is calculated using the rest of the numbers in the ISBN, when checked, the check digit is recalculated, if it produces a different value an error has occurred during data transmission or entry.

1. Hash Totals

Hash totals are meaningless totals calculated using a series of entered records, for example if you find the totals of all the record numbers of a collection of records it is a meaningless total. It could be used as a hash total to validate the records.

1. Control Totals

This is similar to a hash total except the total is a meaningful one, i.e. instead of totaling record numbers you might total the salaries of the employees in an employee database, this total provides some meaning and it can be used to validate data.

Well the above are some of the checks made when you enter data. So the next time you register for a service online remember most of these checks and maybe even a few more are made on each of the fields you fill in!

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