programmers SQL 고득점 Kit - JOIN 문제 코드

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

1. 없어진 기록 찾기

select o.animal_id, o.name
from animal_outs o left outer join animal_ins i
on o.animal_id = i.animal_id
where i.animal_id is null;

2. 있었는데요 없었습니다

select o.animal_id, o.name
from animal_outs o inner join animal_ins i
on o.animal_id = i.animal_id
where o.datetime < i.datetime
order by i.datetime;

3. 오랜 기간 보호한 동물(1)

select i.name, i.datetime
from animal_ins i left outer join animal_outs o
on i.animal_id = o.animal_id
where o.animal_id is null
order by i.datetime limit 3;

4. 보호소에서 중성화한 동물

select i.animal_id, i.animal_type, i.name
from animal_ins i inner join animal_outs o
on i.animal_id = o.animal_id
where i.sex_upon_intake like 'Intact%'
and o.sex_upon_outcome not like 'Intact%'
order by i.animal_id;