Which syntax is appropriate for a self-join on the employees table?

The correct choice effectively demonstrates the proper syntax for performing a self-join on the employees table. In a self-join, the same table is utilized twice in a query to compare rows within that table, typically using table aliases to distinguish between the two instances.

In this case, the syntax specifies the selection of relevant columns, applies both table aliases (which enhances clarity), and uses the correct "inner join" clause to establish the necessary relationship between the two instances of the employees table. Specifically, the use of aliases "e1" and "e2" allows the SQL query to refer to each instance of the employees table distinctly — "e1" represents one group of employees while "e2" represents a second group (often for comparison purposes like employees and their managers).

The syntax "on e1.ID = e2.ID" indicates the condition for the inner join, though in a typical managerial hierarchy, you would likely compare a manager's ID from one alias to an employee's ID from the other alias. This clarity aids in logical comparison, facilitating a self-join scenario.

The other options lack proper syntax or appropriate joins, making them ineffective for achieving the intended self-join. For instance, using "and" instead of "inner