[programmers] MySQL - Lv.3 없어진 기록 찾기 (join)

문제

 

 

 

 

 

 

풀이

 

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;