其中参数2表示保留两位有效数字，但是只负责四舍五入到两位小数，但是不负责截断
Round(number,2)
select round(avg(win_rate),2) pjs from win_rate where miner_id="f030203" and createtime>= now( ) - interval 8 DAY;
拼接
concat("值1"，"值2")
select concat(round(avg(win_rate),2),"%") pjs from win_rate where miner_id="f030203" and createtime>= now( ) - interval 8 DAY;