#修改文件或者文件夹权限
sudo chmod 666 myfile||myfolder （可读写）
sudo chmod 644 myfile||myfolder （只读）
#进入mysql
#先进入root用户
mysql -u root -p
show databases;
use mydb;
show tables;
desc mytable;
#更新表密码
update users set password="yOp4LPKXV5yWY3r3gqnm/j6UBbJhODgx" where user_id ="admin";
update users set school="dhaa1901" where user_id="196197";
update users set user_id="dhccKyc" where user_id ="dhkyc";
update contest set school="dhcc1919" where contest_id =1003;
#设置utf8
#查询编码
mysql> show variables like 'character%'
#修改数据库、表：
ALTER DATABASE `jol` DEFAULT CHARACTER SET utf8 COLLATE utf8_general_ci;
ALTER TABLE `users` DEFAULT CHARACTER SET utf8 COLLATE utf8_general_ci;
#导入数据
LOAD data local infile '/home/you/1901user5.txt' into table users fields terminated by '\t' lines terminated by '\r\n';
LOAD data local infile '/home/you/Downloads/2020OI00.txt' into table users fields terminated by '\t' lines terminated by '\r\n';
LOAD data local infile '/home/you/Downloads/2021user003.txt' into table users fields terminated by '\t' lines terminated by '\r\n';
LOAD data local infile '/home/you/Downloads/2021user003-1.txt' into table users fields terminated by '\t' lines terminated by '\r\n';
#删除数据
delete from users where user_id = "195006";
delete from users where user_id = "dhccadmin";
delete from users where school = "dhuu2099";
delete from privilege where rightstr != "administrator" or rightstr != "source_browser" ;
#退出
quit;
ALTER TABLE solution DROP file_path;
ALTER TABLE solution ADD rec text;
ALTER TABLE solution ADD file_path text;
//最近20天的提交记录
select solution_id, nick,time,memory,in_date,contest_id from solution where (TO_DAYS(NOW())-TO_DAYS(in_date)<20) order by solution_id desc;
