What are the rules enforced on data in a database?

What are the rules enforced on data in a database?

• A. File backups
• B. System backups
• C. Constraints
• D. Stored locally

Answer: (C)

Data integrity in a database is maintained by constraints—the rules that specify what data is allowed and how it relates across the system. These constraints ensure values have the right type, are present when required, are unique, and that relationships between tables stay consistent. Examples include restricting a column to a numeric or date type, requiring a value (NOT NULL), ensuring uniqueness (UNIQUE), identifying each row (PRIMARY KEY), enforcing valid links between tables (FOREIGN KEY), and applying custom conditions (CHECK). The database engine enforces these rules during inserts, updates, and deletes, rejecting any change that would violate them to keep data accurate and reliable. Backup-related concepts like file or system backups or simply where data is stored don’t define the rules governing the data itself.

Data integrity in a database is maintained by constraints—the rules that specify what data is allowed and how it relates across the system. These constraints ensure values have the right type, are present when required, are unique, and that relationships between tables stay consistent. Examples include restricting a column to a numeric or date type, requiring a value (NOT NULL), ensuring uniqueness (UNIQUE), identifying each row (PRIMARY KEY), enforcing valid links between tables (FOREIGN KEY), and applying custom conditions (CHECK). The database engine enforces these rules during inserts, updates, and deletes, rejecting any change that would violate them to keep data accurate and reliable. Backup-related concepts like file or system backups or simply where data is stored don’t define the rules governing the data itself.