题解 | #截取出年龄#
使用join查询方式找出没有分类的电影id以及名称
http://www.nowcoder.com/practice/a158fa6e79274ac497832697b4b83658
select
SUBSTRING_INDEX(SUBSTRING_INDEX(profile,',',-2),',',1) as age,
count(device_id) as number
From user_submit
Group by age
#subtring_index左右两边限制需要嵌套
#也可用substring(profile,12,2)