题解 | #计算25岁以上和以下的用户数量#

# union all的方式：
select '25岁以下', count(*) from user_profile where age<25 or age is null
union all
select '25岁及以上', count(age) from user_profile where age>=25;

# case when的方式：
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
case 
    when age<25 or age is null
    then '25岁以下'
    when age>=25
    then '25岁及以上'
end
;

https://www.nowcoder.com/share/jump/9258278581716292999660

union all 是我想到的方法。不过不如case when的写法更加高级。还是case when 的写法更加高级，也优雅。