Which relational constraint states that no part of a primary key may be null?

Entity integrity is a fundamental principle in relational database management that ensures the uniqueness and validity of primary keys within a table. It specifically requires that every primary key must have a value, meaning that no part of a primary key can be null. This constraint is crucial because primary keys uniquely identify each record in a table, and allowing null values would undermine the ability to reliably distinguish between different records.

Establishing entity integrity ensures the integrity of the database at the table level, fostering consistent and reliable database operations. This constraint thus guarantees that all primary keys are valid and can be used for indexing and building relationships with other tables. By maintaining this integrity, data consistency and accessibility are enhanced, making it easier to manage and retrieve data from the database.

Understanding entity integrity is essential for database design because it lays the groundwork for accurate data relationships and helps prevent data anomalies during database operations.