1.登录mysql

#mysql -u root -p

2.新增用户

insert into mysql.user(Host,User,Password) values("localhost","xxx",password("***"));

注释：xxx为新建用户名，***为用户密码

3.执行该句后，还需要刷新权限表

flush privileges;

4.新建数据库并赋予用户权限
create database dbtest；

全部授权：
允许本地登录
grant all privileges on dbtest.* to xxx@localhost identified by "*";
允许任何主机登录
grant all privileges on dbtest. to xxx@'%' identified by "";
部分授权：
grant select,update on dbtest.* to xxx@localhost identified by "***";

5.赋予权限，还需要再刷新权限表

flush privileges;

6.通过sql语句查询出新增结果

select user,host,password from mysql.user;

7.删除用户

delete from user where user=‘xxx’;
flush privileges;

8.删除数据库

drop database dbtest;

9.修改密码

update mysql.user set password=password(‘新密码’) where User='xxx' and Host='localhost';
flush privileges;