링크: https://leetcode.com/problems/managers-with-at-least-5-direct-reports/
Table: Employee
+-------------+---------+
| Column Name | Type |
+-------------+---------+
| id | int |
| name | varchar |
| department | varchar |
| managerId | int |
+-------------+---------+
id is the primary key (column with unique values) for this table.
Each row of this table indicates the name of an employee, their department, and the id of their manager.
If managerId is null, then the employee does not have a manager.
No employee will be the manager of themself.
Write a solution to find managers with at least five direct reports.
Return the result table in any order.
The result format is in the following example.
Example 1:
Input:
Employee table:
+-----+-------+------------+-----------+
| id | name | department | managerId |
+-----+-------+------------+-----------+
| 101 | John | A | null |
| 102 | Dan | A | 101 |
| 103 | James | A | 101 |
| 104 | Amy | A | 101 |
| 105 | Anne | A | 101 |
| 106 | Ron | B | 101 |
+-----+-------+------------+-----------+
Output:
+------+
| name |
+------+
| John |
+------+
목표: 5명 이상의 직속 부하가 있는 매니저를 찾는 솔루션을 작성
SELECT e1.name
FROM Employee e1
JOIN Employee e2
ON e1.id = e2.managerId
GROUP BY e2.managerId
HAVING COUNT(*) >= 5;
이 문제는 셀프조인을 활용해 풀었다.
e1
테이블과e2
테이블managerId
를 기준으로 GROUP BY 하고,