https://school.programmers.co.kr/learn/courses/30/lessons/132203
DATE_FORMAT을 출력 형식에 맞게 설정해 주어야 한다.
SELECT DR_NAME, DR_ID, MCDP_CD, DATE_FORMAT(HIRE_YMD,'%Y-%m-%d')
FROM DOCTOR
WHERE MCDP_CD = 'CS' OR MCDP_CD = 'GS'
ORDER BY HIRE_YMD DESC, DR_NAME ASC;