The Number Of Employees Which Report To Each Employee Problem

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+-------------+----------+
| Column Name | Type     |
+-------------+----------+
| employee_id | int      |
| name        | varchar  |
| reports_to  | int      |
| age         | int      |
+-------------+----------+
employee_id is the primary key for this table.
This table contains information about the employees and the id of the manager they report to. Some employees do not report to anyone (reports_to is null). 

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Employees table:
+-------------+---------+------------+-----+
| employee_id | name    | reports_to | age |
+-------------+---------+------------+-----+
| 9           | Hercy   | null       | 43  |
| 6           | Alice   | 9          | 41  |
| 4           | Bob     | 9          | 36  |
| 2           | Winston | null       | 37  |
+-------------+---------+------------+-----+

Result table:
+-------------+-------+---------------+-------------+
| employee_id | name  | reports_count | average_age |
+-------------+-------+---------------+-------------+
| 9           | Hercy | 2             | 39          |
+-------------+-------+---------------+-------------+
Alice and Bob report to Hercy, hence Hercy has 2 people report to him, and the average of their age is (41+36)/2 = 38.5 which is 39 after rounding it to the nearest integer.

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select e1.reports_to as employee_id,
       e2.name,
       count(e1.reports_to) as reports_count,
       round(avg(e1.age),0) as average_age
from employees e1
join employees e2
on e1.reports_to=e2.employee_id
group by e1.reports_to
order by e1.reports_to