Data validation refers to checking the content of data to ensure that it satisfies certain rules, known as constraints. For example, the employee name should never be omitted in the employee table, and the delivery date should be after (greater than) the order date.

Any interactive application, whether for opening a bank account, registering an online complaint, or filing income tax, has a form, web page, or static page that interacts with the user, and, typically, with a database. The form or web page is the front-end application, and the database is a back-end application.

The application can validate data either at the front end or at the back end. At the front end, you write code specific to controls in the form. For example, to enforce the rule that the employee name is required, you can disable the form's submit button when the value in the employee name text box is empty or blank. At the back end, you can apply a NOT NULL constraint to the employee name field in the employee table.

Consider the following:

What are the advantages and disadvantages of front-end and back-end validation?

In which specific situations would one technique of validation be preferred over the other?