Chapter 5. Customizing Data Validation

Data validation is one of the most significant responsibilities of line-of-business applications. In fact, an application that accepts input from users needs to validate data before sending it to the back-end database. Think of fields that only accept numeric values: They need to validate the user input to ensure that no alphabetic characters are entered, and then the application must notify the user of validation errors. Modern relational databases usually provide built-in validation rules, such as constraints, null values, or default values. Database validation is important, but in modern data-centric applications it cannot be the only validation mechanism, for several reasons: