Analyze Organization Hierarchy

Problem

Table: Employees

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+----------------+---------+
| Column Name    | Type    | 
+----------------+---------+
| employee_id    | int     |
| employee_name  | varchar |
| manager_id     | int     |
| salary         | int     |
| department     | varchar |
+----------------+----------+
employee_id is the unique key for this table.
Each row contains information about an employee, including their ID, name, their manager's ID, salary, and department.
manager_id is null for the top-level manager (CEO).

Write a solution to analyze the organizational hierarchy and answer the following:

Hierarchy Levels: For each employee, determine their level in the organization (CEO is level 1, employees reporting directly to the CEO are level 2, and so on).
Team Size: For each employee who is a manager, count the total number of employees under them (direct and indirect reports).
Salary Budget: For each manager, calculate the total salary budget they control (sum of salaries of all employees under them, including indirect reports, plus their own salary).

Return the result table ordered by the result ordered bylevel in ascending order, then by budget in descending order, and finally by employee_name in ascending order.

The result format is in the following example.

Examples

Example 1:

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Input:

Employees table:
+-------------+---------------+------------+--------+-------------+
| employee_id | employee_name | manager_id | salary | department  |
+-------------+---------------+------------+--------+-------------+
| 1           | Alice         | null       | 12000  | Executive   |
| 2           | Bob           | 1          | 10000  | Sales       |
| 3           | Charlie       | 1          | 10000  | Engineering |
| 4           | David         | 2          | 7500   | Sales       |
| 5           | Eva           | 2          | 7500   | Sales       |
| 6           | Frank         | 3          | 9000   | Engineering |
| 7           | Grace         | 3          | 8500   | Engineering |
| 8           | Hank          | 4          | 6000   | Sales       |
| 9           | Ivy           | 6          | 7000   | Engineering |
| 10          | Judy          | 6          | 7000   | Engineering |
+-------------+---------------+------------+--------+-------------+
    

Output:
+-------------+---------------+-------+-----------+--------+
| employee_id | employee_name | level | team_size | budget |
+-------------+---------------+-------+-----------+--------+
| 1           | Alice         | 1     | 9         | 84500  |
| 3           | Charlie       | 2     | 4         | 41500  |
| 2           | Bob           | 2     | 3         | 31000  |
| 6           | Frank         | 3     | 2         | 23000  |
| 4           | David         | 3     | 1         | 13500  |
| 7           | Grace         | 3     | 0         | 8500   |
| 5           | Eva           | 3     | 0         | 7500   |
| 9           | Ivy           | 4     | 0         | 7000   |
| 10          | Judy          | 4     | 0         | 7000   |
| 8           | Hank          | 4     | 0         | 6000   |
+-------------+---------------+-------+-----------+--------+

Explanation:

Organization Structure:
- Alice (ID: 1) is the CEO (level 1) with no manager
- Bob (ID: 2) and Charlie (ID: 3) report directly to Alice (level 2)
- David (ID: 4), Eva (ID: 5) report to Bob, while Frank (ID: 6) and Grace (ID: 7) report to Charlie (level 3)
- Hank (ID: 8) reports to David, and Ivy (ID: 9) and Judy (ID: 10) report to Frank (level 4)
Level Calculation:
- The CEO (Alice) is at level 1
- Each subsequent level of management adds 1 to the level
Team Size Calculation:
- Alice has 9 employees under her (the entire company except herself)
- Bob has 3 employees (David, Eva, and Hank)
- Charlie has 4 employees (Frank, Grace, Ivy, and Judy)
- David has 1 employee (Hank)
- Frank has 2 employees (Ivy and Judy)
- Eva, Grace, Hank, Ivy, and Judy have no direct reports (team_size = 0)
Budget Calculation:
- Alice’s budget: Her salary (12000) + all employees’ salaries (72500) = 84500
- Charlie’s budget: His salary (10000) + Frank’s budget (23000) + Grace’s salary (8500) = 41500
- Bob’s budget: His salary (10000) + David’s budget (13500) + Eva’s salary (7500) = 31000
- Frank’s budget: His salary (9000) + Ivy’s salary (7000) + Judy’s salary (7000) = 23000
- David’s budget: His salary (7500) + Hank’s salary (6000) = 13500
- Employees with no direct reports have budgets equal to their own salary

Note:

The result is ordered first by level in ascending order
Within the same level, employees are ordered by budget in descending order then by name in ascending order

Solution

Method 1 – Using Recursive CTE

Intuition

The organization hierarchy forms a tree structure, where each employee points to their manager. By recursively traversing this tree from the CEO (who has no manager), we can assign levels, count subordinates, and sum salaries for each subtree rooted at every employee.

Approach

Build the Hierarchy with Levels:
- Use a recursive CTE to start from the CEO (manager_id IS NULL), assigning level 1.
- For each employee, increment the level by 1 from their manager.
Find All Subordinates:
- Use another recursive CTE to collect, for each manager, all employees in their subtree (direct and indirect reports).
Calculate Team Size and Budget:
- For each employee, count the number of subordinates (excluding themselves) for team_size.
- Sum the salaries of themselves and all their subordinates for budget.
Assemble the Result:
- Join the above results to get employee_id, employee_name, level, team_size, and budget.
- Order by level ASC, budget DESC, employee_name ASC.

Code

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WITH RECURSIVE
-- 1. Build the hierarchy and assign levels
Hierarchy AS (
  SELECT
   employee_id,
   employee_name,
   manager_id,
   salary,
   1 AS level
  FROM Employees
  WHERE manager_id IS NULL
  UNION ALL
  SELECT
   e.employee_id,
   e.employee_name,
   e.manager_id,
   e.salary,
   h.level + 1
  FROM Employees e
  JOIN Hierarchy h ON e.manager_id = h.employee_id
),
-- 2. For each employee, find all subordinates (including themselves)
Subtree AS (
  SELECT
   employee_id AS manager_id,
   employee_id AS subordinate_id
  FROM Employees
  UNION ALL
  SELECT
   s.manager_id,
   e.employee_id
  FROM Subtree s
  JOIN Employees e ON e.manager_id = s.subordinate_id
),
-- 3. Calculate team_size and budget for each employee
TeamBudget AS (
  SELECT
   s.manager_id AS employee_id,
   COUNT(*) - 1 AS team_size, -- exclude self
   SUM(e.salary) AS budget
  FROM Subtree s
  JOIN Employees e ON s.subordinate_id = e.employee_id
  GROUP BY s.manager_id
)
SELECT
  h.employee_id,
  h.employee_name,
  h.level,
  tb.team_size,
  tb.budget
FROM Hierarchy h
JOIN TeamBudget tb ON h.employee_id = tb.employee_id
ORDER BY h.level ASC, tb.budget DESC, h.employee_name ASC;

Complexity

⏰ Time complexity: O(n^2) (Each employee may be traversed for every manager in the worst case, e.g., a chain hierarchy.)
🧺 Space complexity: O(n^2) (The Subtree CTE can have up to n^2 rows in the worst case.)

Problem#

Examples#

Solution#

Method 1 – Using Recursive CTE#

Intuition#

Approach#

Code#

Complexity#