[다시보기]GROUP BY - 언어별 개발자 분류하기

https://school.programmers.co.kr/learn/courses/30/lessons/276036

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with developer_skill as (
    select * from developers left join skillcodes on skill_code & code = code
)

select 
case
    when group_concat(category, ",") like "%Front End%" and group_concat(name, ",") like "%Python%" then "A"
    when group_concat(name, ",") like "%C#%" then "B"
    when group_concat(category, ",") like "%Front End%" then "C"
end as grade, id, email
from developer_skill
group by id, email
having grade is not null
order by grade,id