select student_id,avg(number)
from `score`
group by student_id
having avg(number)>60
为表添加索引
(foreign key (team_id) references t_team(id) );
mysql 时间格式
date_format(add_time,'%Y-%m-%d %H:%i:%s') as addtime 时分秒显示
设置mysql连接数量
show variables like 'max_connections';
set GLOBAL max_connections=10000000;