我要评论如果我们只能使用 root 用户，这样存在安全隐患。这时，就需要使用 mysql 的用户管理。
1. 用户
1.1 用户信息
mysql> show databases; +--------------------+ | database | +--------------------+ | d1 | | information_schema | | mysql | <--用户信息所在的数据库 | oj_system | | performance_schema | | scott | | store | | sys | | test_db | | users | +--------------------+ 10 rows in set (0.00 sec) mysql> use mysql reading table information for completion of table and column names you can turn off this feature to get a quicker startup with -a database changed mysql> select host,user,authentication_string from user; +-----------+------------------+------------------------------------------------------------------------+ | host | user | authentication_string | +-----------+------------------+------------------------------------------------------------------------+ | localhost | debian-sys-maint | $a$005$ ad?>}~yyxg9covu8bmtohesua4r2l8vdbyqciw5ghvas89xcjdaqga3 | | localhost | mysql.infoschema | $a$005$thisisacombinationofinvalidsaltandpasswordthatmustneverbrbeused | | localhost | mysql.session | $a$005$thisisacombinationofinvalidsaltandpasswordthatmustneverbrbeused | | localhost | mysql.sys | $a$005$thisisacombinationofinvalidsaltandpasswordthatmustneverbrbeused | | localhost | root | | | localhost | wsj | | +-----------+------------------+------------------------------------------------------------------------+ 6 rows in set (0.00 sec)
user 表的表结构：
mysql> desc user;
+--------------------------+-----------------------------------+------+-----+-----------------------+-------+
| field | type | null | key | default | extra |
+--------------------------+-----------------------------------+------+-----+-----------------------+-------+
| host | char(255) | no | pri | | |
| user | char(32) | no | pri | | |
| select_priv | enum('n','y') | no | | n | |
| insert_priv | enum('n','y') | no | | n | |
| update_priv | enum('n','y') | no | | n | |
| delete_priv | enum('n','y') | no | | n | |
| create_priv | enum('n','y') | no | | n | |
| drop_priv | enum('n','y') | no | | n | |
| reload_priv | enum('n','y') | no | | n | |
| shutdown_priv | enum('n','y') | no | | n | |
| process_priv | enum('n','y') | no | | n | |
| file_priv | enum('n','y') | no | | n | |
| grant_priv | enum('n','y') | no | | n | |
| references_priv | enum('n','y') | no | | n | |
| index_priv | enum('n','y') | no | | n | |
| alter_priv | enum('n','y') | no | | n | |
| show_db_priv | enum('n','y') | no | | n | |
| super_priv | enum('n','y') | no | | n | |
| create_tmp_table_priv | enum('n','y') | no | | n | |
| lock_tables_priv | enum('n','y') | no | | n | |
| execute_priv | enum('n','y') | no | | n | |
| repl_slave_priv | enum('n','y') | no | | n | |
| repl_client_priv | enum('n','y') | no | | n | |
| create_view_priv | enum('n','y') | no | | n | |
| show_view_priv | enum('n','y') | no | | n | |
| create_routine_priv | enum('n','y') | no | | n | |
| alter_routine_priv | enum('n','y') | no | | n | |
| create_user_priv | enum('n','y') | no | | n | |
| event_priv | enum('n','y') | no | | n | |
| trigger_priv | enum('n','y') | no | | n | |
| create_tablespace_priv | enum('n','y') | no | | n | |
| ssl_type | enum('','any','x509','specified') | no | | | |
| ssl_cipher | blob | no | | null | |
| x509_issuer | blob | no | | null | |
| x509_subject | blob | no | | null | |
| max_questions | int unsigned | no | | 0 | |
| max_updates | int unsigned | no | | 0 | |
| max_connections | int unsigned | no | | 0 | |
| max_user_connections | int unsigned | no | | 0 | |
| plugin | char(64) | no | | caching_sha2_password | |
| authentication_string | text | yes | | null | |
| password_expired | enum('n','y') | no | | n | |
| password_last_changed | timestamp | yes | | null | |
| password_lifetime | smallint unsigned | yes | | null | |
| account_locked | enum('n','y') | no | | n | |
| create_role_priv | enum('n','y') | no | | n | |
| drop_role_priv | enum('n','y') | no | | n | |
| password_reuse_history | smallint unsigned | yes | | null | |
| password_reuse_time | smallint unsigned | yes | | null | |
| password_require_current | enum('n','y') | yes | | null | |
| user_attributes | json | yes | | null | |
+--------------------------+-----------------------------------+------+-----+-----------------------+-------+
51 rows in set (0.00 sec)字段解释：
- host：表示这个用户可以从哪个主机登陆，如果是localhost，表示只能从本机登陆
- user：用户名
- authentication_string：用户密码通过password函数加密后的
- *_priv：用户拥有的权限。
1.2 创建用户
create user '用户名'@'登陆主机/ip' identified by '密码';
例子：
mysql> create user wsj@localhost identified by '123456'; query ok, 0 rows affected (0.01 sec) mysql> select user,host from user; +------------------+-----------+ | user | host | +------------------+-----------+ | debian-sys-maint | localhost | | mysql.infoschema | localhost | | mysql.session | localhost | | mysql.sys | localhost | | root | localhost | | wsj | localhost | <--新创建的用户 +------------------+-----------+ 6 rows in set (0.00 sec)
登录试试：
wsj@izuf6dza8bf7vp0zjipnhmz:~$ mysql -uwsj -hlocalhost -p enter password: welcome to the mysql monitor. commands end with ; or \g. your mysql connection id is 186 server version: 8.0.46-0ubuntu0.22.04.3 (ubuntu) copyright (c) 2000, 2026, oracle and/or its affiliates. oracle is a registered trademark of oracle corporation and/or its affiliates. other names may be trademarks of their respective owners. type 'help;' or '\h' for help. type '\c' to clear the current input statement. mysql>
备注：可能实际在设置密码的时候，因为mysql本身的认证等级比较高，一些简单的密码无法设置，会爆出如下报错：
-- error 1819 (hy000): your password does not satisfy the current policy requirements
-- 解决方案参考：https://www.jb51.net/program/32588081w.htm
--查看密码设置相关要求：show variables like 'validate_password%';
不要轻易添加一个可以从任意地方登陆的 user：
create user '用户名'@'%' identified by '密码';
1.3 删除用户
drop user '用户名'@'主机名';
例子：
mysql> select user,host from user; +------------------+-----------+ | user | host | +------------------+-----------+ | debian-sys-maint | localhost | | mysql.infoschema | localhost | | mysql.session | localhost | | mysql.sys | localhost | | root | localhost | | wsj | localhost | +------------------+-----------+ 6 rows in set (0.00 sec) # 直接给个用户名，不能删除，它默认是%，表示所有地方可以登陆的用户。 mysql> drop user wsj; error 1396 (hy000): operation drop user failed for 'wsj'@'%' mysql> drop user wsj@localhost; query ok, 0 rows affected (0.01 sec) mysql> select user,host from user; +------------------+-----------+ | user | host | +------------------+-----------+ | debian-sys-maint | localhost | | mysql.infoschema | localhost | | mysql.session | localhost | | mysql.sys | localhost | | root | localhost | +------------------+-----------+ 5 rows in set (0.00 sec)
1.4 修改用户密码
自己改自己的密码
set password=password('新密码');
root 用户修改指定用户的密码
set password for '用户名'@'主机名'=password('新密码');
mysql 8.0 以后移除了 password() 函数，可以使用下面的方法：
-- 修改当前登录用户的密码
alter user current_user() identified by '密码';
-- 指定用户名修改
alter user '用户名'@'登录主机' identified by '密码';
mysql> alter user current_user() identified by '111'; query ok, 0 rows affected (0.01 sec)
执行后通常会自动生效，也可以手动刷新以下权限(root)：
flush privileges;
2. 数据库的权限
mysql 数据库提供的权限列表：
2.1 给用户授权
刚创建的用户没有任何权限，需要给用户授权
grant 权限列表 on 库.对项名(表名) to '用户名'@'登陆位置' [identified by '密码'（用户还没创建的时候带）];
权限列表，多个权限用逗号分开
grant select on ... grant select, delete, create on .... grant all [privileges] on ... -- 表示赋予该用户在该对象上的所有权限
- *.*：代表本系统中的所有数据库的所有对象（表，视图，存储过程等）
- 库.*：表示某个数据库中的所有数据对象（表，视图，存储过程等）
- identified by 可选。如果用户存在，赋予权限的同时修改密码，如果该用户不存在，就是创建用户（mysql 8.0 以后不再支持 grant 时自动创建用户，必须先用 create user 创建用户，再用 grant 授权）
如果发现赋权限后，没有生效，可以刷新一下（root）：
flush privileges;
2.2 回收权限
revoke 权限列表 on 库.对项名 from '用户名'@'登陆位置';
例子：
-- 回收 wsj 对 test 数据库的所有权限 -- root 身份，终端a mysql> revoke all on test.* from 'wsj'@'localhost'; query ok, 0 rows affected (0.00 sec) --whb身份，终端b mysql> show databases; +--------------------+ | database | +--------------------+ | information_schema | | test | +--------------------+ 2 rows in set (0.00 sec) mysql> show databases; +--------------------+ | database | +--------------------+ | information_schema | +--------------------+ 1 row in set (0.00 sec)
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