26. Explain the difference between optimistic concurrency control and pessimistic concurrency control with respect to database updates
27. What feature introduced with SQL Server 2005 provides a way to define temporary tabular result sets that, while similar to derived tables, can be self-referencing and can be referenced multiple time sin the same query?
28. Imagine a database table named 'employee' that contains the columns "ID", "Name", "Salary", and "Department". Explain the concept of a correlated subquery, and provide a brief query that would list the names of all employees who have a salary higher than the average for their department using a correlated subquery.
29. What is dependency injection, and how might it be useful for building unit tests in a large application?
30. What is inversion of control, and how is it useful in addressing cross-cutting concerns?