# select if(age>=25,'25岁及以上','25岁以下') as age_cnt, count(*) as number
# from user_profile
# group by age_cnt;

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

参考题解。

主要注意语法的使用。

if(条件，结果1，结果2)

(case when 条件 then 结果1

else 结果2 end)

count（*）语句是在group by执行完分组后再执行。