修改mysql库里边的user表：
update mysql.user set host=‘localhost‘ where user=‘root‘;

刷新权限：
flush privileges;

编辑my.cnf
vim /usr/local/mysql/my.cnf 


==================
[client]
default-character-set=utf8
[mysqld]
character_set_server=utf8
datadir=/usr/local/mysql/data
port = 3306
sql_mode=NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES
symbolic-links=0
max_connections=400
innodb_file_per_table=1
#表名大小写不明感，敏感为
lower_case_table_names=1
#跳过权限表，添加该命令
skip-grant-tables 

service mysql restart

mysql -uroot -p


直接回车不用输入密码！！！！！！！！
然后使用下面3种修改密码之一即可

格式：
set password for 用户名@ip =password(‘密码‘);
alter user ‘用户‘@‘ip‘ identified by ‘密码‘;

刷新权限：
flush privileges;

示例
set password for root@127.0.0.1 = password(‘root‘);

格式：
./mysqladmin -u用户 -p旧密码 password 新密码

格式：
select * from mysql.user where user=‘root‘ \G;

update mysql.user set authentication_string=password(‘123456‘) where user=‘root‘;

刷新权限：
flush privileges;

语法：
create user ‘用户名‘@‘ip‘ identified by ‘密码‘;

用户名：创建的账户
ip：指定该用户在哪个主机上可以登录，如果是本地用户可用localhost，如果想让该用户可以在任意远程主机登录，可以使用通配符：%
密码：该用户的登录密码，密码可以为空，如果为空，则该用户可以不需要密码登录服务器

查看权限：
show grants for ‘用户名‘@‘ip‘;

查看用户权限：
select * from mysql.user where user=‘用户‘ \G;

mysql> select * from mysql.user where user=‘ybchen‘ \G;
*************************** 1. row ***************************
                  Host: %
                  User: ybchen
           Select_priv: N
           Insert_priv: N
           Update_priv: N
           Delete_priv: N
           Create_priv: N
             Drop_priv: N
           Reload_priv: N
         Shutdown_priv: N
          Process_priv: N
             File_priv: N
            Grant_priv: N
       References_priv: N
            Index_priv: N
            Alter_priv: N
          Show_db_priv: N
            Super_priv: N
 Create_tmp_table_priv: N
      Lock_tables_priv: N
          Execute_priv: N
       Repl_slave_priv: N
      Repl_client_priv: N
      Create_view_priv: N
        Show_view_priv: N
   Create_routine_priv: N
    Alter_routine_priv: N
      Create_user_priv: N
            Event_priv: N
          Trigger_priv: N
Create_tablespace_priv: N
              ssl_type: 
            ssl_cipher: 
           x509_issuer: 
          x509_subject: 
         max_questions: 0
           max_updates: 0
       max_connections: 0
  max_user_connections: 0
                plugin: mysql_native_password
 authentication_string: *D2EDE838B7E0B05A2C599D3E1F5821D0ADC4F26E
      password_expired: N
 password_last_changed: 2020-11-19 23:26:12
     password_lifetime: NULL
        account_locked: N
1 row in set (0.00 sec)

create user ‘ybchen‘@‘172.20.%.%‘ identified by ‘123456‘;

语法：
drop user ‘用户‘@‘ip‘;

语法：
delete from mysql.user where user=‘用户‘;

语法：
grant 权限1,权限2... on 数据库 to ‘用户‘
grant 权限1,权限2... on 数据库 to ‘用户‘@‘ip‘ identified by ‘密码‘

all privileges：代表所有权限
*.*：代表所有库所有表

grant all privileges on *.* to ‘cyb‘;

语法：
创建用户
create user ‘cyb2‘@‘%‘ identified by ‘cyb2‘;
授予cyb2用户，db1库的所有权限
grant all privileges on db1.* to ‘cyb2‘@‘%‘ identified by ‘cyb2‘;
刷新权限
flush privileges;

语法：
创建用户
create user ‘cyb3‘@‘%‘ identified by ‘cyb3‘;
授予cyb3用户，db1库student，增删改查权限
grant select,update,delete on db1.student to ‘cyb3‘@‘%‘ identified by ‘cyb3‘;
刷新权限
flush privileges;

语法：
revoke 权限1,权限2... on 数据库对象 from ‘用户‘@‘ip‘

revoke all privileges on *.* from ‘cyb‘@‘%‘;
flush privileges;