mysql -u 'username' -p'password' //用户名和密码直接换掉,-p和密码中间没有space.

insert into mysql.user(Host,User,Password) values("localhost","test",password("1234"));
//修改test 和 密码

delete from mysql.user Where User='test' and Host='localhost';
//以用户名和host为目标选择

select user,host from mysql.user; //查看用户user和host信息

update mysql.user set password=password('新密码') where User="test" and Host="localhost";
//修改密码
update mysql.user set host='%' where User="test";
//修改host,'%'表示外部主机可以连接,'localhost'表示只能本机连接.

grant select,delete,update,create,drop on basename.* to "username"@"%" identified by "1234"; // 或者all privileges
//在"basename"数据库中,赋予username以上权利,密码要付在后面.

show databases; //显示所有数据库
drop database dataname; //删除指定数据库
drop table tablename; //删除指定表