Query tuning involves analyzing and modifying SQL queries to make them more efficient in terms of execution time and resource usage. This process often involves examining query execution plans, indexing strategies, and data retrieval methods to optimize performance.

Checksums are a method used to detect errors in data transmission or storage by calculating a unique value based on the content of the data. Comparing checksums before and after transmission or storage helps identify any changes or corruption that may have occurred.

Data consistency and accuracy are crucial aspects of database testing. Implementing data validation checks ensures that the data entered into the database meets certain criteria, thus maintaining consistency and accuracy. This involves validating data types, constraints, and relationships to ensure they adhere to predefined standards. Performing data reconciliation helps identify discrepancies between different datasets or systems, aiding in maintaining data accuracy.

A SELF JOIN is a regular join but with a table being joined to itself. In this scenario, you can use a SELF JOIN on the employee table, matching the ManagerID in the table to the ID of another employee to retrieve the names of all employees and their respective managers.

In a subquery, the EXISTS operator can be used to compare a single value with a result set. The EXISTS operator returns true if the subquery returns any rows, otherwise false. It is commonly used in correlated subqueries to check for the existence of a particular condition. For example, you can use EXISTS to check if there are any employees in a department with a certain job title.

Load testing involves gradually increasing the load to observe how the system performs, whereas stress testing involves pushing the system beyond its limits to identify breaking points.

Database testing aids organizations in adhering to data compliance and regulatory requirements. By testing databases, organizations can ensure that their data handling practices align with legal standards and industry regulations, reducing the risk of non-compliance penalties and data breaches.

The role of a test plan in the database testing process is to define the scope and objectives of testing. It outlines what aspects of the database will be tested, the testing approach, the resources required, and the schedule for testing activities. A well-defined test plan helps ensure that all necessary tests are conducted, and that testing efforts are focused on achieving the desired quality goals for the database system.

SQLUnit: SQLUnit is a database testing tool specifically designed for unit testing of SQL queries. It provides a framework for writing and executing unit tests for SQL code, helping developers ensure the correctness and reliability of their SQL queries.

Functional testing is the type of SQL testing that verifies the correctness of SQL queries. It ensures that the SQL queries perform the intended operations accurately and return the expected results. Functional testing involves testing individual functions or features of the software to validate their behavior according to the specified requirements.