The Number of Employees Which Report to Each Employee _ Easy. LeetCode *

 

Solution

SELECT 
    e.employee_id,
    e.name,
    COUNT(r.employee_id) AS reports_count,
    ROUND(AVG(r.age), 0) AS average_age
FROM 
    Employees e
JOIN 
    Employees r
ON 
    e.employee_id = r.reports_to
GROUP BY 
    e.employee_id, e.name
ORDER BY 
    e.employee_id;

 

처음에는 다 구할 수 있었지만 reports_to에 대응하는 name을 찾을 수 없어서 검색해야만 했다. 확인해 보니 간단하게 JOIN으로 해결할 수 있었다...