select age,count(*) as 'number' from (select case when birthday>=20070000 and birthday<=20170000 then '1-10岁' when birthday>=19970000 and birthday<=20070000 then '11-20岁' when birthday>=19870000 and birthday<=19970000 then '21-30岁' when birthday>=19670000 and birthday<=19870000 then '31-40岁' ELSE '未知' end as age from wk_user_info)a group by age 这是SQL