select substring_index(substring_index(profile,',',-2),',',1) as age,
  //截取中间字符串：substring_index(substring_index())此函数灵活套娃可以解决
  //强调：正负数：是指从左向右？从右向左截取几个字符串 而不是第几个！！！！！！！
       count(*) as number
from user_submit 
group by age;