Limiting access to predefined queries is the control that would prevent the users from obtaining an individual employee’s salary, if they only require access rights that allow them to view the average salary of groups of employees. A query is a request for information from a database, which can be expressed in a structured query language (SQL) or a graphical user interface (GUI). A query can specify the criteria, conditions, and operations for selecting, filtering, sorting, grouping, and aggregating the data from the database. A predefined query is a query that has been created and stored in advance by the database administrator or the data owner, and that can be executed by the authorized users without any modification. A predefined query can provide several benefits, such as:

Improving the performance and efficiency of the database by reducing the processing time and resources required for executing the queries

Enhancing the security and confidentiality of the database by restricting the access and exposure of the sensitive data to the authorized users and purposes

Increasing the accuracy and reliability of the database by preventing the errors or inconsistencies that might occur due to the user input or modification of the queries

Reducing the cost and complexity of the database by simplifying the query design and management

Limiting access to predefined queries is the control that would prevent the users from obtaining an individual employee’s salary, if they only require access rights that allow them to view the average salary of groups of employees, because it can ensure that the users can only access the data that is relevant and necessary for their tasks, and that they cannot access or manipulate the data that is beyond their scope or authority. For example, a predefined query can be created and stored that calculates and displays the average salary of groups of employees based on certain criteria, such as department, position, or experience. The users who need to view this information can execute this predefined query, but they cannot modify it or create their own queries that might reveal the individual employee’s salary or other sensitive data.

The other options are not the controls that would prevent the users from obtaining an individual employee’s salary, if they only require access rights that allow them to view the average salary of groups of employees, but rather controls that have other purposes or effects. Segregating the database into a small number of partitions each with a separate security level is a control that would improve the performance and security of the database by dividing it into smaller and manageable segments that can be accessed and processed independently and concurrently. However, this control would not prevent the users from obtaining an individual employee’s salary, if they have access to the partition that contains the salary data, and if they can create or modify their own queries. Implementing Role Based Access Control (RBAC) is a control that would enforce the access rights and permissions of the users based on their roles or functions within the organization, rather than their identities or attributes. However, this control would not prevent the users from obtaining an individual employee’s salary, if their roles or functions require them to access the salary data, and if they can create or modify their own queries. Reducing the number of people who have access to the system for statistical purposes is a control that would reduce the risk and impact of unauthorized access or disclosure of the sensitive data by minimizing the exposure and distribution of the data. However, this control would not prevent the users from obtaining an individual employee’s salary, if they are among the people who have access to the system, and if they can create or modify their own queries.