题解 | #计算25岁以上和以下的用户数量#

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

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 '25岁以下' as age_cut,count(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(device_id) as number
from user_profile
where age>=25;