题解 | #分群并计算群体人数#

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