A . Only the second statement will display departments with no employees. This is true because the second statement uses a LEFT JOIN to include all departments from the departments table, even those without matching entries in the employees table. When there are no employees in a department, the AVG(salary) will be NULL, and the department will still be displayed1.
C . Both statements will execute successfully if you add e.avg_sal to the select list. This is correct. Both statements calculate e.avg_sal as an average salary, either through a subquery or a join operation. Adding e.avg_sal to the select list will display the average salary alongside the departments. However, it's important to note that the first statement will not display departments with no employees because it does not use a join that would allow for NULL values from the employees table2.
Reference:
Understanding SQL JOINs - Stack Overflow1.
Oracle Documentation on JOIN Operations2.
Note: The other options are incorrect because:
B . The first statement will not display departments with no employees since it does not use a join that includes departments without matching employee records.
D . As explained, the first statement will not display departments with no employees.
E . There is a typo in the option; it should be E.AVG_SAL. Even if corrected, the first statement alone would not execute successfully because it does not include a join to bring in the avg_sal value.
F . The second statement will display departments with no employees, but the first statement will not, so this option is incorrect.