题解 | #截取出年龄#
截取出年龄
http://www.nowcoder.com/practice/b8d8a87fe1fc415c96f355dc62bdd12f
select
substring_index(substring_index(profile, ',',3), ',', -1) as age,
//先截取出(a,b,c),再截取出 c
count(device_id) as number
from
user_submit
group by
age
//注意很多次写对了但不通过都是因为用了中文的括号