What is the purpose of the AFTER UPDATE block predicate in SQL Server?

The AFTER UPDATE block predicate in SQL Server is utilized primarily to enforce business rules by preventing unauthorized data modifications. This functionality allows database administrators and developers to implement specific conditions that must be met before an update operation is permitted. When this predicate is applied, if an update does not satisfy the defined criteria, it will be rejected, thereby ensuring that only authorized changes to the data can occur.

In the context of database security and integrity, this is crucial as it helps maintain accurate and trustworthy data within the system. By enforcing rules at this level, it minimizes the risk of unintentional or malicious changes that could compromise the application's reliability or the quality of the data.

The other options focus on different aspects: logging updates or changes to structure, which is not the primary role of predicates; or optimizing query performance, which is not relevant to the function of AFTER UPDATE predicates. Therefore, the emphasis on preventing unauthorized data modifications accurately captures the purpose of the AFTER UPDATE block predicate in SQL Server.