[프로그래머스] 12세 이하인 여자 환자 목록 출력하기

https://school.programmers.co.kr/learn/courses/30/lessons/132201

IFNULL

혹은 IF & ISNULL 문제

-- SOLUTION 1
SELECT PT_NAME, PT_NO, GEND_CD, AGE, IFNULL(TLNO, 'NONE') AS TLNO
FROM PATIENT
WHERE AGE <= 12 AND GEND_CD='W'
ORDER BY AGE DESC, PT_NAME


-- SOLUTION 2
SELECT PT_NAME, PT_NO, GEND_CD, AGE, IF(ISNULL(TLNO), 'NONE', TLNO) AS TLNO
FROM PATIENT
WHERE AGE <= 12 AND GEND_CD='W'
ORDER BY AGE DESC, PT_NAME