.create user user1@'localhost' identified  by '';

.insert into mysql.user(user,host,password,ssl_cipher,x509_issuer,x509_subject) values('user2','localhost',password(''),'','','');

.grant select on *.* to user3@'localhost' identified by '' //授select权所有库和所有表给user3，密码123
flush privileges

.drop user user1@'localhost'

.delete from mysql.user where user='user1' and host='localhost';

.mysqladmin -uroot -proot password ''

.update mydql.user set password=password('new_password') where user='root' and host='localhost';

.set password=password('new_password')
flush privileges //刷新授权表

.set password for user3@'localhost' =password('new_password');

flush privileges;

.updatae mysql.user set password=password('new_password') where user='user3' and host='localhost';

flush privileges;

.grant select on *.* to user3@'localhost' identified by 'pwd';

flush privileges;

set password=password('new_password');

vim /etc/my.cnf

skip-grant-tables//将这句话的注释去掉

service mysqld restart

mysql -uroot //然后就可以跳过权限表进入mysql

update mysql.user set password=password('new_password') where user='user3' and host='localhost';

flush privileges;

\q   //退出mysql

vim /etc/my.cnf

#skip-grant-tables //将这句话再重新注释

grant option: 授权选项

max_queries_per_hour:定义每小时允许执行的查询数

max_updates_per_hou:定义每小时允许执行的更新数

max_connections_per-hour:定义每小时可以建立的连接数

max-user_connections:定义单个用户同是可以建立的连接数

grant all on *.* to admin1@'%' identified by 'password';

grant all on *.* to admin2@'%' identified by 'pw' with grant option;

grant all on *.* bbs.* to admin3@'%' identified by 'pw';

grant all on bbs.user to admin4@'%' identified by 'pw';

grant select(col1),insert(col2,col3) on bbs.user to admin5@'%' identified by 'pw';

flush privileges

show grants for admin@'%' \G;

.revoke delete on *.* from admin@'%';//回收部分权限

.revoke all privileges on *.* from admin@'%';

revoke grant on *.* from admin@'%'; //回收全部权限(包括授权)
flush privileges;    //刷新授权