mysql if和ifnull 使用

SELECT age_range,count(*) FROM 
(SELECT IF(IFNULL(age,0)>=25,"25岁及以上","25岁以下") as age_range,device_id FROM  user_profile) AS user_profile
GROUP BY age_range

SELECT IF(IFNULL(age,0)>=25,"25岁及以上","25岁以下") as age_range,count(*) FROM  user_profile GROUP BY age_range