What is the general purpose of database constraints such as NOT NULL, UNIQUE, and CHECK?

What is the general purpose of database constraints such as NOT NULL, UNIQUE, and CHECK?

• A. To protect data quality by enforcing rules at the database level.
• B. To accelerate query execution plans.
• C. To enforce replication across regions.
• D. To reduce storage requirements.

Answer: (A)

Constraints like NOT NULL, UNIQUE, and CHECK are mechanisms to enforce data validity right where data is stored. They protect data quality by defining rules that must be satisfied for every insert or update, so invalid or inconsistent data can’t creep in. NOT NULL ensures a value is present, preventing missing data in a field that must have information. UNIQUE guarantees that each value (or combination of values) is distinct, which is essential for identifiers or any business rule that requires uniqueness. CHECK lets you express custom conditions that data must meet, such as a positive price or a date within a certain range. Because these checks are enforced by the database itself, they hold true across all applications and processes that touch the data, ensuring consistency and integrity even in complex, multi-user environments. Other options describe benefits like performance, replication, or storage efficiency, which aren’t the primary purpose of these constraints.

Constraints like NOT NULL, UNIQUE, and CHECK are mechanisms to enforce data validity right where data is stored. They protect data quality by defining rules that must be satisfied for every insert or update, so invalid or inconsistent data can’t creep in.

NOT NULL ensures a value is present, preventing missing data in a field that must have information. UNIQUE guarantees that each value (or combination of values) is distinct, which is essential for identifiers or any business rule that requires uniqueness. CHECK lets you express custom conditions that data must meet, such as a positive price or a date within a certain range. Because these checks are enforced by the database itself, they hold true across all applications and processes that touch the data, ensuring consistency and integrity even in complex, multi-user environments.

Other options describe benefits like performance, replication, or storage efficiency, which aren’t the primary purpose of these constraints.