题解 | 某乎问答高质量的回答中用户属于各级别的数量

with c as(select a.answer_date, a.author_id, a.issue_id, a.char_len, b.author_level,
case when b.author_level in (1,2) then "1-2级"
     when b.author_level in (3,4) then "3-4级"
     else "5-6级" end  level_cut
from answer_tb a left join author_tb b on a.author_id=b.author_id
where a.char_len>=100)
select level_cut, count(*) num 
from c
group by 1
order by 2 desc