题解 | #查找某个年龄段的用户信息#
查看不同年龄段的用户明细
http://www.nowcoder.com/practice/ae44b2b78525417b8b2fc2075b557592
基于列的逻辑表达式，CASE表达式.可以用在SELECT,UPDATE,DELETE,SET以及IN,WHERE,ORDER BY和HAVING子句之后;
select device_id,gender,
case
when age >= 20 and age<= 24 then "20-24岁"
when age >= 25 then "25岁以上"
else "其他"
end as age_cut
from user_profile group by device_id;
