题解 | 截取出年龄
截取出年龄
https://www.nowcoder.com/practice/b8d8a87fe1fc415c96f355dc62bdd12f
select substring_index(substring_index(profile,',',3),',',-1) as age,count(*) as number from user_submit group by age
substring_index进行两次运算,第二次是在第一次的提取基础上再运算的,所以应该是-1