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3236. CEO Subordinate Hierarchy 🔒

Description

Table: Employees

++
\| Column Name   \| Type    \|
++
\| employee_id   \| int     \|
\| employee_name \| varchar \|
\| manager_id    \| int     \|
\| salary        \| int     \|
++
employee_id is the unique identifier for this table.
manager_id is the employee_id of the employee's manager. The CEO has a NULL manager_id.

Write a solution to find subordinates of the CEO (both direct and indirect), along with their level in the hierarchy and their salary difference from the CEO.

The result should have the following columns:

The query result format is in the following example.

  • subordinate_id: The employee_id of the subordinate
  • subordinate_name: The name of the subordinate
  • hierarchy_level: The level of the subordinate in the hierarchy (1 for direct reports, 2 for their direct reports, and so on)
  • salary_difference: The difference between the subordinate's salary and the CEO's salary

Return the result table ordered by hierarchy_level ascending, and then by subordinate_id ascending.

The query result format is in the following example.

 

Example:

Input:

Employees table:

+-++
\| employee_id \| employee_name  \| manager_id \| salary  \|
+-++
\| 1           \| Alice          \| NULL       \| 150000  \|
\| 2           \| Bob            \| 1          \| 120000  \|
\| 3           \| Charlie        \| 1          \| 110000  \|
\| 4           \| David          \| 2          \| 105000  \|
\| 5           \| Eve            \| 2          \| 100000  \|
\| 6           \| Frank          \| 3          \| 95000   \|
\| 7           \| Grace          \| 3          \| 98000   \|
\| 8           \| Helen          \| 5          \| 90000   \|
+-++

Output:

+-+++-+
\| 2              \| Bob              \| 1                \| -30000            \|
\| 3              \| Charlie          \| 1                \| -40000            \|
\| 4              \| David            \| 2                \| -45000            \|
\| 5              \| Eve              \| 2                \| -50000            \|
\| 6              \| Frank            \| 2                \| -55000            \|
\| 7              \| Grace            \| 2                \| -52000            \|
\| 8              \| Helen            \| 3                \| -60000            \|
+----+

Explanation:

  • Bob and Charlie are direct subordinates of Alice (CEO) and thus have a hierarchy_level of 1.
  • David and Eve report to Bob, while Frank and Grace report to Charlie, making them second-level subordinates (hierarchy_level 2).
  • Helen reports to Eve, making Helen a third-level subordinate (hierarchy_level 3).
  • Salary differences are calculated relative to Alice's salary of 150000.
  • The result is ordered by hierarchy_level ascending, and then by subordinate_id ascending.

Note: The output is ordered first by hierarchy_level in ascending order, then by subordinate_id in ascending order.

Solutions

Solution 1: Recursive CTE + Join

First, we use a recursive CTE to calculate the hierarchy level of each employee, where the CEO’s level is $0$. We save employee_id, employee_name, hierarchy_level, manager_id, and salary into a temporary table T.

Then, we query the CEO’s salary and save it into a temporary table P.

Finally, we join tables T and P to calculate the salary difference for each subordinate, and sort by hierarchy_level and subordinate_id.

  • # Write your MySQL query statement below
WITH RECURSIVE
    T AS (
        SELECT
            employee_id,
            employee_name,
            0 AS hierarchy_level,
            manager_id,
            salary
        FROM Employees
        WHERE manager_id IS NULL
        UNION ALL
        SELECT
            e.employee_id,
            e.employee_name,
            hierarchy_level + 1 AS hierarchy_level,
            e.manager_id,
            e.salary
        FROM
            T t
            JOIN Employees e ON t.employee_id = e.manager_id
    ),
    P AS (
        SELECT salary
        FROM Employees
        WHERE manager_id IS NULL
    )
SELECT
    employee_id subordinate_id,
    employee_name subordinate_name,
    hierarchy_level,
    t.salary - p.salary salary_difference
FROM
    T t
    JOIN P p
WHERE hierarchy_level != 0
ORDER BY 3, 1;

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