题解 | #分群并计算群体人数#

select
    age_group,
    count(age_group) as user_count
from
    (
        select
            case
                when age < 20 then '20以下'
                when age >= 20
                and age <= 50 then '20-50'
                when age > 50 then '50以上'
                else '未填写'
            end age_group
        from
            customers_info
    ) a
group by
    age_group