What does Uniqueness guarantee in data modeling?

What does Uniqueness guarantee in data modeling?

• A. Requires each real-world instance to be represented only once in the data collection.
• B. All values in a column must be unique.
• C. The data must be accurate.
• D. The data must be consistent across tables.

Answer: (A)

Uniqueness in data modeling means you avoid representing the same real-world entity more than once in a dataset. This is typically enforced with a primary key or a unique constraint on the row identifier, ensuring there is one and only one record for each real-world instance. It’s not about every value in a column being unique—that would be a separate, narrower constraint on that attribute and would be too restrictive for most data. It also doesn’t by itself guarantee data accuracy or cross-table consistency, which are separate quality and integrity concerns.

Uniqueness in data modeling means you avoid representing the same real-world entity more than once in a dataset. This is typically enforced with a primary key or a unique constraint on the row identifier, ensuring there is one and only one record for each real-world instance. It’s not about every value in a column being unique—that would be a separate, narrower constraint on that attribute and would be too restrictive for most data. It also doesn’t by itself guarantee data accuracy or cross-table consistency, which are separate quality and integrity concerns.