题解 | 某乎问答高质量的回答中用户属于各级别的数量（傻瓜做法）

select * 
from
(select 
'5-6级' as level_cut,
sum(if(author_level = 5 or author_level = 6,1,0)) as num
from answer_tb left join author_tb using(author_id)
where char_len >= 100
union
select 
'3-4级' as level_cut,
sum(if(author_level = 3 or author_level = 4,1,0)) as num
from answer_tb left join author_tb using(author_id)
where char_len >= 100
union
select 
'1-2级' as level_cut,
sum(if(author_level = 1 or author_level = 2,1,0)) as num
from answer_tb left join author_tb using(author_id)
where char_len >= 100) t1
where num != 0
order by num desc,level_cut

没啥好说的，挺傻的