programmers [SQL] : JOIN

programmers.co.kr/learn/courses/30/parts/17046

프로그래머스

1. 없어진 기록 찾기

-- 코드를 입력하세요
SELECT A.animal_id , A.name
from animal_outs A left join animal_ins B on A.animal_id= B.animal_id
where B.animal_id is null
order by A.animal_id

2. 있었는데요 없었습니다.

select A.animal_id,A.name
from animal_ins A , animal_outs B
where A.animal_id = B.animal_id and
    A.datetime > B.datetime
order by A.datetime

3. 오랜 기간 보호한 동물(1)

select A.name ,A.datetime
from animal_ins A left join animal_outs B on A.animal_id  = B.animal_id
where B.animal_id is null
order by A.datetime

limit 3

4. 보호소에서 중성화한 동물

select A.animal_id, A.animal_type, A.name
from animal_ins A ,animal_outs B 
where A.animal_id = B.animal_id 
and A.sex_upon_intake !=B.sex_upon_outcome
order by A.animal_id

funny SQL~