新建用户：

mysql>use mysql;
mysql>insert into user(user,host,authentication_string) values('test','%',password('1234'));
mysql>flush privileges;

退出登录试验一下。

修改用户密码：

mysql>use mysql;
mysql>update user set authentication_string=password('123456') where user='test';
mysql>flush privileges;

删除用户：

mysql>use mysql;
mysql>delete from user where user='test' and host='localhost';
mysql>flush privileges;

授权用户数据库权限：

mysql>grant all privileges on testDB.* to test@localhost identified by '1234';
mysql>flush privileges;

授权用户数据库部分权限：

mysql>grant select,update on testDB.* to test@localhost identified by '1234';
mysql>flush privileges;

授权用户远程登录：

mysql>grant select,updateon testDB.* to test@"%" identified by '1234';
mysql>flush privileges;