the-number-of-employees-which-report-to-each-employee

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Database

Table: <code>Employees</code>

<pre>
+-------------+----------+
| Column Name | Type |
+-------------+----------+
| employee_id | int |
| name | varchar |
| reports_to | int |
| age | int |
+-------------+----------+
employee_id is the column with unique values 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). 
</pre>

&nbsp;

For this problem, we will consider a manager an employee who has at least 1 other employee reporting to them.

Write a solution to report the ids and the names of all managers, the number of employees who report directly to them, and the average age of the reports rounded to the nearest integer.

Return the result table ordered by <code>employee_id</code>.

The&nbsp;result format is in the following example.

&nbsp;
Example 1:

<pre>
Input: 
Employees table:
+-------------+---------+------------+-----+
| employee_id | name | reports_to | age |
+-------------+---------+------------+-----+
| 9 | Hercy | null | 43 |
| 6 | Alice | 9 | 41 |
| 4 | Bob | 9 | 36 |
| 2 | Winston | null | 37 |
+-------------+---------+------------+-----+
Output: 
+-------------+-------+---------------+-------------+
| employee_id | name | reports_count | average_age |
+-------------+-------+---------------+-------------+
| 9 | Hercy | 2 | 39 |
+-------------+-------+---------------+-------------+
Explanation: Hercy has 2 people report directly to him, Alice and Bob. Their average age is (41+36)/2 = 38.5, which is 39 after rounding it to the nearest integer.
</pre>

Example 2:

<pre>
Input: 
Employees table:
+-------------+---------+------------+-----+ 
| employee_id | name &nbsp; &nbsp;| reports_to | age |
|-------------|---------|------------|-----|
| 1 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; | Michael | null &nbsp; &nbsp; &nbsp; | 45 &nbsp;|
| 2 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; | Alice &nbsp; | 1 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;| 38 &nbsp;|
| 3 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; | Bob &nbsp; &nbsp; | 1 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;| 42 &nbsp;|
| 4 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; | Charlie | 2 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;| 34 &nbsp;|
| 5 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; | David &nbsp; | 2 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;| 40 &nbsp;|
| 6 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; | Eve &nbsp; &nbsp; | 3 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;| 37 &nbsp;|
| 7 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; | Frank &nbsp; | null &nbsp; &nbsp; &nbsp; | 50 &nbsp;|
| 8 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; | Grace &nbsp; | null &nbsp; &nbsp; &nbsp; | 48 &nbsp;|
+-------------+---------+------------+-----+ 
Output: 
+-------------+---------+---------------+-------------+
| employee_id | name &nbsp; &nbsp;| reports_count | average_age |
| ----------- | ------- | ------------- | ----------- |
| 1 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; | Michael | 2 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; | 40 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;|
| 2 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; | Alice &nbsp; | 2 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; | 37 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;|
| 3 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; | Bob &nbsp; &nbsp; | 1 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; | 37 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;|
+-------------+---------+---------------+-------------+

</pre>

count_employees

The Number of Employees Which Report to Each Employee

表：<code>Employees</code>

<pre>
+-------------+----------+
| Column Name | Type |
+-------------+----------+
| employee_id | int |
| name | varchar |
| reports_to | int |
| age | int |
+-------------+----------+
employee_id 是这个表中具有不同值的列。
该表包含员工以及需要听取他们汇报的上级经理的 ID 的信息。 有些员工不需要向任何人汇报（reports_to 为空）。
</pre>

&nbsp;

对于此问题，我们将至少有一个其他员工需要向他汇报的员工，视为一个经理。

编写一个解决方案来返回需要听取汇报的所有经理的 ID、名称、直接向该经理汇报的员工人数，以及这些员工的平均年龄，其中该平均年龄需要四舍五入到最接近的整数。

返回的结果集需要按照&nbsp;<code>employee_id</code> 进行排序。

结果的格式如下：

&nbsp;

示例 1:

<pre>
输入：
Employees 表：
+-------------+---------+------------+-----+
| employee_id | name | reports_to | age |
+-------------+---------+------------+-----+
| 9 | Hercy | null | 43 |
| 6 | Alice | 9 | 41 |
| 4 | Bob | 9 | 36 |
| 2 | Winston | null | 37 |
+-------------+---------+------------+-----+
输出：
+-------------+-------+---------------+-------------+
| employee_id | name | reports_count | average_age |
+-------------+-------+---------------+-------------+
| 9 | Hercy | 2 | 39 |
+-------------+-------+---------------+-------------+
解释：
Hercy 有两个需要向他汇报的员工, 他们是 Alice and Bob. 他们的平均年龄是 (41+36)/2 = 38.5, 四舍五入的结果是 39.
</pre>

示例 2:

<pre>
输入： 
Employees 表：
+-------------+---------+------------+-----+ 
| employee_id | name &nbsp; &nbsp;| reports_to | age |
|-------------|---------|------------|-----|
| 1 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; | Michael | null &nbsp; &nbsp; &nbsp; | 45 &nbsp;|
| 2 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; | Alice &nbsp; | 1 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;| 38 &nbsp;|
| 3 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; | Bob &nbsp; &nbsp; | 1 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;| 42 &nbsp;|
| 4 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; | Charlie | 2 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;| 34 &nbsp;|
| 5 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; | David &nbsp; | 2 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;| 40 &nbsp;|
| 6 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; | Eve &nbsp; &nbsp; | 3 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;| 37 &nbsp;|
| 7 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; | Frank &nbsp; | null &nbsp; &nbsp; &nbsp; | 50 &nbsp;|
| 8 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; | Grace &nbsp; | null &nbsp; &nbsp; &nbsp; | 48 &nbsp;|
+-------------+---------+------------+-----+ 
输出： 
+-------------+---------+---------------+-------------+
| employee_id | name &nbsp; &nbsp;| reports_count | average_age |
| ----------- | ------- | ------------- | ----------- |
| 1 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; | Michael | 2 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; | 40 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;|
| 2 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; | Alice &nbsp; | 2 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; | 37 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;|
| 3 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; | Bob &nbsp; &nbsp; | 1 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; | 37 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;|
+-------------+---------+---------------+-------------+</pre>