How To Apply Filtering Criteria at Group Level?

If you want to return only specific groups from the query, you can apply filtering criteria at the
group level by using the HAVING clause inside the GROUP BY clause. The following script gives
you a good HAVING example:
SQL> SELECT department_id, MIN(salary), MAX(salary), AVG(salary)
FROM employees GROUP BY department_id HAVING AVG(salary) < 5000;
DEPARTMENT_ID MIN(SALARY) MAX(SALARY) AVG(SALARY)
------------- ----------- ----------- -----------
30 2500 11000 4150
50 2100 8200 3475.55556
10 4400 4400 4400