Database Security and Integrity

Databases often store sensitive and valuable data — personal information, financial records, medical data. Protecting this data from unauthorised access, corruption, and loss is a critical responsibility. This lesson covers the key concepts of database security and data integrity.

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Data Integrity

Data integrity means that the data stored in the database is accurate, consistent, and reliable. There are several types:

1. Entity Integrity

Every table must have a primary key, and no primary key value can be NULL. This ensures every record is uniquely identifiable.

2. Referential Integrity

Every foreign key value must either match an existing primary key in the referenced table or be NULL (if the field allows NULLs). This ensures that relationships between tables remain valid.

Example: If you try to insert an order with a CustomerID that does not exist in the Customers table, the database will reject the insert.

3. Domain Integrity

Every value in a field must conform to the defined data type, format, and constraints for that field.