[leetcode][sql] leftJoin - on - where - orderby-

Employees Whose Manager Left the Company

# Write your MySQL query statement below
# 조건:
# 급여가 30000미만
# 매니저가 회사를 떠남(manager_id는 있지만 해당 employee_id가 테이블에 없음)
SELECT e1.employee_id
FROM Employees e1
LEFT JOIN Employees e2 ON e1.manager_id = e2.employee_id
WHERE e1.salary < 30000 
  AND e1.manager_id IS NOT NULL  -- 매니저가 있어야 함
  AND e2.employee_id IS NULL     -- 하지만 매니저 정보는 없어야 함
ORDER BY e1.employee_id;

#leetcode #sql #leftjoin