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(*) as number
# from user_profile
# where age<25 or age is null

# union

# select '25岁及以上' as age_cut,count(*) as number
# from user_profile
# where age>=25


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,count(*) as number
from user_profile
group by age_cut

添加计算列后使用group by函数