题解 | 某乎问答高质量的回答中用户属于各级别的数量

select 
    case when au.author_level in (5,6) then '5-6级'
    when au.author_level in (3,4) then '3-4级'
    when au.author_level in (1,2) then '1-2级'
    end as level_cnt, count(issue_id) as num
from 
    author_tb au join answer_tb an
on 
    au.author_id = an.author_id
where 
    an.char_len > 100
group by 
    level_cnt
order by 
    num desc