Employees Earning More Than Their Managers

Description:

Write a solution to find the employees who earn more than their managers. Return the result table in any order.

Table: Employee

Column Name	Type
id	int
name	varchar
salary	int
managerId	int

id is the primary key for this table. Each row of this table indicates the ID of an employee, their name, salary, and the ID of their manager.

Example 1: Input: Employee table:

id	name	salary	managerId
1	Joe	70000	3
2	Henry	80000	4
3	Sam	60000	Null
4	Max	90000	Null

Output:

Employee
Joe

Explanation: Joe is the only employee who earns more than his manager.

---

Approaches:

1. Self-Join

We can join the Employee table to itself to compare an employee's salary directly with their manager's salary. By matching an employee's managerId to another employee's id (who acts as the manager), we can filter for cases where the employee's salary is strictly greater.

• Time Complexity: $O(N)$ or $O(N \log N)$ depending on the database engine's join implementation and available indexing.
• Space Complexity: $O(N)$ to store the final result set.

Self-Join Solutions:

MySQL / PostgreSQL

SELECT 
    e1.name AS Employee
FROM 
    Employee e1
JOIN 
    Employee e2 
ON 
    e1.managerId = e2.id
WHERE 
    e1.salary > e2.salary;