题解 | #计算25岁以上和以下的用户数量#

select
    if (age >= 25, "25岁及以上", "25岁以下") as age_cut,
/*
(case 
when age >= 25 then "25岁及以上" 
else "25岁以下" end) as age_cut,
*/
    count(gender) as number
from
    user_profile
group by
    age_cut;

条件判断写在SELECT子句里，包括if子句和case when子句,if子句if后跟（），case when 子句整体在（）里