Describe and use methods of data validation

6.2 Data Integrity

What is Data Integrity?

Data integrity means that the data stored in a system is accurate, consistent, and reliable. Think of it like a lockbox that keeps your secrets safe – if the lockbox is broken, the secrets can be lost or corrupted.

Common Causes of Data Loss

• Human error – typing the wrong value.
• Hardware failure – a bad hard drive.
• Software bugs – a program that writes wrong data.
• Security breaches – malicious actors tampering with data.

Methods of Data Validation

1. Input Validation – Check that the data entered by a user matches the expected type.

   Example: A phone number must contain only digits and be 10 digits long.

2. Format Validation – Ensure the data follows a specific pattern.

   Example: An email address must contain @ and a domain.

3. Range Validation – Confirm that numeric values lie within a valid interval.

   Example: age must satisfy $0 \leq \text{age} \leq 120$.

4. Consistency Checks – Verify that related data fields agree with each other.

   Example: The startDate must be before the endDate.

5. Referential Integrity – Ensure that relationships between tables are maintained.

   Example: A student_id in the grades table must exist in the students table.

Practical Example – Validation Table

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