[26.02.10 코테(MySQL)]-부서별 평균 연봉 조회하기

Lv3. 부서별 평균 연봉 조회하기 (MySQL)

링크: https://school.programmers.co.kr/learn/courses/30/lessons/284529
 
내가 작성한 코드

-- 풀이1
SELECT D.DEPT_ID, D.DEPT_NAME_EN, ROUND(AVG(E.SAL)) AS AVG_SAL
FROM HR_DEPARTMENT D
JOIN HR_EMPLOYEES E
  ON D.DEPT_ID = E.DEPT_ID
GROUP BY D.DEPT_ID, D.DEPT_NAME_EN
ORDER BY AVG_SAL DESC;

-- 풀이2 (USING)
SELECT DEPT_ID, DEPT_NAME_EN, ROUND(AVG(SAL)) AS AVG_SAL
FROM HR_DEPARTMENT 
JOIN HR_EMPLOYEES 
USING (DEPT_ID)
GROUP BY DEPT_ID, DEPT_NAME_EN
ORDER BY AVG_SAL DESC;

-- 풀이3 (서브쿼리)
SELECT D.DEPT_ID, D.DEPT_NAME_EN, E.AVG_SAL
FROM HR_DEPARTMENT D
JOIN (SELECT DEPT_ID, ROUND(AVG(SAL)) AS AVG_SAL
      FROM HR_EMPLOYEES
      GROUP BY DEPT_ID) E
  ON D.DEPT_ID = E.DEPT_ID
ORDER BY AVG_SAL DESC;