Which statement about data types and domain constraints is true?

• A. Data types guarantee business logic automatically
• B. Data types store actual data values only
• C. Data types enforce referential integrity
• D. Data types ensure values fit expected formats and ranges according to business rules

Answer: (D)

Data types control what kind of data can be stored and the basic boundaries the values must meet, such as format and range. They ensure entries conform to the expected type—dates must be valid dates, numbers must be numeric, and decimals have defined precision and scale. This alignment with expected formats and ranges helps enforce the business rules at the data level, acting as a first line of validation.

Data types do not automatically enforce all business logic beyond those basic constraints, nor do they ensure referential integrity (that’s handled by keys and relationships). They also aren’t only about storing values; they define what kinds of values are permissible in the first place.