How does a relational database ensure data integrity?

How a relational database ensures data integrity:

• Schema constraints: data types, NOT NULL, UNIQUE, PRIMARY KEY, and CHECK constraints ensure stored values meet required rules.

• Referential integrity: FOREIGN KEY constraints keep relationships consistent so linked rows cannot be left dangling or invalid.

• Transactions and ACID properties: atomicity, consistency, isolation, and durability ensure changes are applied reliably and leave the database in a consistent state.

• Triggers and stored procedures: enforce business rules and validate or adjust data when changes occur.

• Access controls: user privileges and role-based permissions prevent unauthorized modifications that could corrupt data.

Examples:

• A PRIMARY KEY prevents duplicate rows; a UNIQUE constraint prevents duplicate values in a column.

• A FOREIGN KEY prevents deleting a parent row while child rows still reference it, preserving referential integrity.

• A transaction groups multiple updates so either all succeed or none do, avoiding partial updates that could leave data inconsistent.

Why the other statements are incorrect:

• "By encrypting all data stored" addresses confidentiality and access protection, not the enforcement of correct values or relationships.

• "By compressing data for efficient storage" improves storage use and possibly performance but does not validate or enforce correctness of data.

• "By allowing unrestricted access to all users" would increase the risk of incorrect or malicious changes and therefore undermine integrity; access controls are required.