题解 | #计算25岁以上和以下的用户数量#

(select 
"25岁以下" as age_cut,
count(distinct device_id) as number
from user_profile
where age < 25 or age is null)
union all 
(select 
"25岁及以上" as age_cut,
count(distinct device_id) as number
from user_profile
where age >= 25)

更智慧的解法
select
    (case when age >= 25 then "25岁及以上" else "25岁以下" end) as age_cut,
     count(*) as number
from user_profile
group by age_cut

记录一下更加智慧的解法