https://school.programmers.co.kr/learn/courses/30/lessons/59403
https://school.programmers.co.kr/learn/courses/30/lessons/59404
https://school.programmers.co.kr/learn/courses/30/lessons/59408
https://school.programmers.co.kr/learn/courses/30/lessons/59405
https://school.programmers.co.kr/learn/courses/30/lessons/59407
20240917===========================================
# SQL Lv 1. 동물의 아이디와 이름
SELECT ANIMAL_ID, NAME
FROM ANIMAL_INS
ORDER BY ANIMAL_ID;
# SQL Lv 1. 여러기준으로 정렬하기
SELECT ANIMAL_ID,NAME,DATETIME
FROM ANIMAL_INS
ORDER BY NAME, DATETIME DESC;
# SQL Lv 1. 상위 N개 레코드
SELECT NAME
FROM ANIMAL_INS
ORDER BY DATETIME
LIMIT 1;
# SQL Lv 1. 이름이 있는 동물의 아이디
SELECT ANIMAL_ID
FROM ANIMAL_INS
WHERE NAME IS NOT NULL;
# SQL Lv 2. 중복 제거하기
SELECT COUNT(DISTINCT NAME) AS count
FROM ANIMAL_INS
WHERE NAME IS NOT NULL;
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