Nesting Group Functions in Oracle SQL

Topic Introduction: In Oracle SQL, nesting group functions involve using multiple functions within a single SQL statement to perform calculations or operations on data. It's a common practice to use functions like SUM, MAX, MIN, AVG, etc., within other functions to perform more complex calculations. Group functions can be nested to a depth of two functions. 

Here's an example of nesting group functions in Oracle SQL, that display the maximum average salary:

Example-01:

SELECT MAX(AVG(salary))

FROM employees

GROUP BY department_id;

In the example, we have used the employees' table and calculated the average salary for each department_id and then displayed the maximum average salary.

Note that the GROUP BY clause is mandatory when nesting group functions.

This is a simple example, but nesting group functions can be used in various scenarios to perform more complex calculations or aggregations based on your specific requirements within Oracle SQL. Always remember to properly structure the SQL statements and handle the nested functions to ensure the desired results.