[Leetcode] Employees With Missing Information

문제 링크

정답

SELECT E.employee_id
FROM Employees E
LEFT JOIN Salaries S
ON E.employee_id = S.employee_id
WHERE S.employee_id IS NULL

UNION

SELECT S.employee_id
FROM Employees E
RIGHT JOIN Salaries S
ON E.employee_id = S.employee_id
WHERE E.employee_id IS NULL

ORDER BY employee_id

✅ Point

• MySQL에선 FULL OUTER JOIN 을 지원하지 않음
• LEFT JOIN + NULL UNION RIGHT JOIN + NULL 으로 접근
• 마지막에 ORDER BY를 작성해 UNION 한 결과를 바탕으로 정렬 수행