题解 | #某乎问答高质量的回答中用户属于各级别的数量#

case when .. then .. else .. when .. then .. else .. end

select level_cut,count(issue_id) num
from(select a.author_id,a.issue_id
        ,(case when b.author_level = 1 or b.author_level = 2 then '1-2级' 
			when  b.author_level = 3 or b.author_level = 4 then '3-4级'
			when  b.author_level = 5 or b.author_level = 6 then '5-6级' end) level_cut
FROM
	(select * from answer_tb where char_len>=100)a 
	join author_tb b on a.author_id=b.author_id
 )a   
group by level_cut
order by num desc