题解 | #计算25岁以上和以下的用户数量#

select age_cut,count(age_cut) as number
from
-- 子查询
(select *,
(case when age<25 or age is null then'25岁以下'
when age>=25 then'25岁及以上'
end) as age_cut
from user_profile) as a
group by age_cut;