题解 | #计算25岁以上和以下的用户数量#

if与 case when ... end 都可以用来做判断

select if(age>=25,'25岁及以上','25岁以下' ) as age_cut,
count(device_id) as number
from user_profile
group by age_cut

select age_cut,count(device_id)as number 
from(Select if(age>=25,'25岁及以上','25岁以下' )as age_cut,device_id 
From user_profile)u2
Group by age_cut
链接：https://www.nowcoder.com/questionTerminal/30f9f470390a4a8a8dd3b8e1f8c7a9fa
来源：牛客网

select (case when age>=25 then '25岁及以上' else '25岁以下' end) as age_cut, 
count(device_id) as number
from user_profile
group by age_cut