Difficulty: Medium

Average Score: 57%

What is true of the data values contained in a primary key?

Rationale

It cannot contain null or blank values.

A primary key uniquely identifies each record in a database table, ensuring that no two records can share the same key value. To maintain this uniqueness, primary keys must not contain null or blank values, as these would undermine the integrity of the database by allowing ambiguity in record identification.

A (It cannot contain name values) YOUR ANSWER

This statement is incorrect because primary keys can indeed contain name values, as long as they are unique and not null. For instance, a primary key could be a person's name if it is guaranteed to be unique across the dataset. The content type of the primary key is not restricted to numeric values.

B (It cannot contain null or blank values) CORRECT

This statement is correct because a primary key must have a valid value that uniquely identifies a record. Null or blank values would violate the requirement for each key to be distinct and identifiable, making this statement a fundamental rule of primary keys in relational databases.

C (It cannot contain zero values) YOUR ANSWER

This statement is misleading because a primary key can contain a value of zero, provided that it is unique and not null. Zero is a valid integer, and if it serves as a unique identifier, it can function as a primary key. The restriction is not on the presence of zero but rather on null or duplicate values.

D (It cannot contain number values) YOUR ANSWER

This statement is incorrect because primary keys can certainly contain number values. Numeric values can be used as primary keys, such as IDs or serial numbers, as long as they maintain uniqueness and do not include null values. The type of value is flexible, depending on the database design.

Conclusion

In summary, a primary key is essential for ensuring each record in a database table is uniquely identifiable, and it must not contain null or blank values. While it can include a variety of data types, including names and numbers, the critical requirement is that it must always hold a unique and valid value. Understanding these characteristics is vital for effective database design and integrity.

Related Questions

View all