mysql 8.0 创建新的数据库、用户并授权，以及相关查看并删除操作
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参考技术A以创建wordpress网站的数据库为例
1、创建数据库
创建可指定字符，或者不指定字符，如果不指定字符，默认为 utf8mb4 和 utf8mb4_0900_ai_ci
2、创建用户
可自行指定用户可访问的IP地址范围。
3、授权用户
4、直接一步到位
或者 这种方法 ：创建并授权用户，是二和三的合并。
1、查看数据库
show databases可查询所有存在的数据库
2、查看用户信息
用户信息在系统数据库mysql中的user表中。密码查询不会显示明文密码，而是显示为加密后的密文。
3、查看用户权限
有两种方式查看。
第一种方式 ： show grants for \'userwordpress\';
第二种方式： select * from mysql.user where user=\'userwordpress\'G;
g 相当于’;’
G使每个字段打印到单独的行，也有 ’;\' 的作用
只能查出哪个数据库的哪张表的权限，如查userwordpress在mysql数据库的user表的权限，显示都是N（no），没有权限，如果查root用户就都是Y（yes）选择了。
用drop而非delete，简单的区分就是，drop是删除【表】，truncate与delete则是删除表中【记录】。
删除用户
同理，删除数据库
用drop删除时，会有确认信息，为了防止误删。（删库跑路，请谨慎操作）
MySQL的授权
grant 授权
什么是用户授权：在数据库服务器上添加新的连接用户，并设置权限和密码。
为什么要用授权：如果没有授权用户，那么只能有root用户在本机登陆数据库，其它用户无法登陆。
没有授权时，其它主机也无法访问数据库。
指令格式:
mysql> grant 权限列表 on 库名 to 用户名@"客户端地址" identified by "密码" ;
权限列表:
all 所有权限
usage 只能连接上数据库，没有任何权限
select,update,inseret ... 个别权限，这个权限对所有字段有效
select,update(字段1,字段2...) 只能对指定的字段有相应的权
库名:
*.* 所有库所有表
库名.* 一个库
库名.表名 一张表
用户名:
授权时可以自定义,要有标识性,容易记,可以名中看出用途存储在mysql库的user表里
客户端地址:
% 表示互联网上的所有主机0
192.168.4.% 网段内的所有主机
192.168.4.1 1台主机
localhost 数据库服务器本机
授权举例1:
添加admin用户,允许从192.168.4.0/24网段连接,对db3库的user表有查询权限,密码为123456
mysql> grant select on db3.user to admin@"192.168.4.%" identified by "123456";
授权举例2:
添加admin2,允许从本机连接,允许以db3库的所有表有 查询,更新,插入删除记录权限,密码为123456
mysql> grant select ,insert,update,delete on db3.* to admin2@"localhost" identified by "123456";
授权库
grant授权的信息是保存在授权库中的，mysql库记录了授权信息，主要的表如下：
user 记录已有的授权用户及权限
db 记录已有授权用户对数据库的访问权限
tables_priv 记录已有授权用户对表的访问权限
columns_priv 记录已有授权用户对字段的访问权限
一 查看当前columns_priv，tables_priv,db,user表中的授权用户
mysql> select user,host,db,table_name,column_name from mysql.columns_priv;
Empty set (0.00 sec) #columns_priv表当前为空，说明当前数据库没有真对某些字段的授权
mysql> select user,host,db,table_name from mysql.tables_priv;
+-----------+-----------+-----+------------+ #tables_priv表中只有系统默认的授权用户msyql.sys
| user | host | db | table_name |
+-----------+-----------+-----+------------+
| mysql.sys | localhost | sys | sys_config |
+-----------+-----------+-----+------------+
mysql> select user,host,db from mysql.db;
+-----------+-----------+-----+ #db表中也是系统默认授权用户mysql.sys
| user | host | db |
+-----------+-----------+-----+
| mysql.sys | localhost | sys |
+-----------+-----------+-----+
mysql> select user,host from mysql.user;
+-----------+-----------+ #user表中有系统默认用户mysql.sys和root
| user | host |
+-----------+-----------+
| mysql.sys | localhost |
| root | localhost |
+-----------+-----------+
二 添加真对school.student表中“学号”，“姓名”，“性别”这三个字段的授权用户col_user
mysql> grant select,update(学号,姓名,性别),insert on school.student to col_user@‘%‘ identified by "123456";
mysql> select user,host,db,table_name,column_name from mysql.columns_priv;
#在columns_priv表中查看授权用户,每条记录是一个授权字段
+----------+------+--------+------------+-------------+
| user | host | db | table_name | column_name |
+----------+------+--------+------------+-------------+
| col_user | % | school | student | 姓名 |
| col_user | % | school | student | 学号 |
| col_user | % | school | student | 性别 |
+----------+------+--------+------------+-------------+
mysql> select user,host,db,table_name from mysql.tables_priv;
+-----------+-----------+--------+------------+ #在tables_priv表中也可以看到该用户对school.student表有访问权限
| user | host | db | table_name | #具体权限需要用show grants查看
+-----------+-----------+--------+------------+
| col_user | % | school | student |
| mysql.sys | localhost | sys | sys_config |
+-----------+-----------+--------+------------+
mysql> show grants for col_user@‘%‘; #通过show grants查看col_user对school.student的具体权限
+-----------------------------------------------------------------------------------------------+
| Grants for col_user@% |
+-----------------------------------------------------------------------------------------------+
| GRANT USAGE ON *.* TO ‘col_user‘@‘%‘ |
| GRANT SELECT, INSERT, UPDATE (性别, 学号, 姓名) ON `school`.`student` TO ‘col_user‘@‘%‘ |
+-----------------------------------------------------------------------------------------------+
mysql> select user,host,db from mysql.db;
+-----------+-----------+-----+ #db表中看不到该用户
| user | host | db |
+-----------+-----------+-----+
| mysql.sys | localhost | sys |
+-----------+-----------+-----+
mysql> select user,host from mysql.user;
+-----------+-----------+ #在user表中可以看到该用户
| user | host |
+-----------+-----------+
| col_user | % |
| mysql.sys | localhost |
| root | localhost |
+-----------+-----------+
mysql>
三 添加授权用户tab_user1,tab_user2对表school.teacher，school.student的访问权限
mysql> grant all on school.teacher to tab_user1@‘%‘ identified by "123456";
mysql> grant select on school.student to tab_user2@‘%‘ identified by "123456";
mysql> select user,host,db,table_name,column_name from mysql.columns_priv;
#colunm_priv表中授权记录的用户没有变化
+----------+------+--------+------------+-------------+
| user | host | db | table_name | column_name |
+----------+------+--------+------------+-------------+
| col_user | % | school | student | 姓名 |
| col_user | % | school | student | 学号 |
| col_user | % | school | student | 性别 |
+----------+------+--------+------------+-------------+
#tables_priv表中可以看到tab_user1,tab_user2用户
mysql> select user,host,db,table_name from mysql.tables_priv;
+-----------+-----------+--------+------------+
| user | host | db | table_name |
+-----------+-----------+--------+------------+
| col_user | % | school | student |
| tab_user1 | % | school | teacher |
| tab_user2 | % | school | student |
| mysql.sys | localhost | sys | sys_config |
+-----------+-----------+--------+------------+
mysql> show grants for tab_user1@‘%‘; #通过show grants可以看出tab_user1,tab_user2的具体授权权限
+---------------------------------------------------------------+
| Grants for tab_user1@% |
+---------------------------------------------------------------+
| GRANT USAGE ON *.* TO ‘tab_user1‘@‘%‘ |
| GRANT ALL PRIVILEGES ON `school`.`teacher` TO ‘tab_user1‘@‘%‘ |
+---------------------------------------------------------------+
mysql> show grants for tab_user2@‘%‘;
+-------------------------------------------------------+
| Grants for tab_user2@% |
+-------------------------------------------------------+
| GRANT USAGE ON *.* TO ‘tab_user2‘@‘%‘ |
| GRANT SELECT ON `school`.`student` TO ‘tab_user2‘@‘%‘ |
+-------------------------------------------------------+
mysql> select user,host,db from mysql.db; #db表中没有变化
+-----------+-----------+-----+
| user | host | db |
+-----------+-----------+-----+
| mysql.sys | localhost | sys |
+-----------+-----------+-----+
mysql> select user,host from mysql.user; #user表中可以看到tab_user1,tab_user2
+-----------+-----------+
| user | host |
+-----------+-----------+
| col_user | % |
| tab_user1 | % |
| tab_user2 | % |
| mysql.sys | localhost |
| root | localhost |
+-----------+-----------+
mysql>
四 添加授权用户db_user1,db_user2用户对库school,school2的访问权限
mysql> grant all on school.* to db_user1@‘%‘ identified by "123456";
mysql> grant select on school2.* to db_user2@‘%‘ identified by "123456";
mysql> select user,host,db,table_name,column_name from mysql.columns_priv;
#只要没有对任意表中字段的授权，column_priv表不会有变化
+----------+------+--------+------------+-------------+
| user | host | db | table_name | column_name |
+----------+------+--------+------------+-------------+
| col_user | % | school | student | 姓名 |
| col_user | % | school | student | 学号 |
| col_user | % | school | student | 性别 |
+----------+------+--------+------------+-------------+
mysql> select user,host,db,table_name from mysql.tables_priv;
#添加了真对库的授权用户，没有对表的授权用户所以db表中也不会变化
+-----------+-----------+--------+------------+
| user | host | db | table_name |
+-----------+-----------+--------+------------+
| col_user | % | school | student |
| tab_user1 | % | school | teacher |
| tab_user2 | % | school | student |
| mysql.sys | localhost | sys | sys_config |
+-----------+-----------+--------+------------+
mysql> select user,host,db from mysql.db; #db表中可以看到添加的授权用户
+-----------+-----------+---------+
| user | host | db |
+-----------+-----------+---------+
| db_user1 | % | school |
| db_user2 | % | school2 |
| mysql.sys | localhost | sys |
+-----------+-----------+---------+
mysql> select user,host from mysql.user; #只要添加了授权用户user表中都会有记录
+-----------+-----------+
| user | host |
+-----------+-----------+
| col_user | % |
| db_user1 | % |
| db_user2 | % |
| tab_user1 | % |
| tab_user2 | % |
| mysql.sys | localhost |
| root | localhost |
+-----------+-----------+
mysql>
五 添加授权用户user对所有库和表有访问权限
mysql> grant all on *.* to user@‘%‘ identified by "123456";
mysql> select user,host,db,table_name,column_name from mysql.columns_priv;
+----------+------+--------+------------+-------------+
| user | host | db | table_name | column_name |
+----------+------+--------+------------+-------------+
| col_user | % | school | student | 姓名 |
| col_user | % | school | student | 学号 |
| col_user | % | school | student | 性别 |
+----------+------+--------+------------+-------------+
3 rows in set (0.00 sec)
mysql> select user,host,db,table_name from mysql.tables_priv;
+-----------+-----------+--------+------------+
| user | host | db | table_name |
+-----------+-----------+--------+------------+
| col_user | % | school | student |
| tab_user1 | % | school | teacher |
| tab_user2 | % | school | student |
| mysql.sys | localhost | sys | sys_config |
+-----------+-----------+--------+------------+
4 rows in set (0.01 sec)
mysql> select user,host,db from mysql.db;
+-----------+-----------+---------+
| user | host | db |
+-----------+-----------+---------+
| db_user1 | % | school |
| db_user2 | % | school2 |
| mysql.sys | localhost | sys |
+-----------+-----------+---------+
3 rows in set (0.00 sec)
mysql> select user,host from mysql.user; #只有在user表中可以看到use_user
+-----------+-----------+
| user | host |
+-----------+-----------+
| col_user | % |
| db_user1 | % |
| db_user2 | % |
| tab_user1 | % |
| tab_user2 | % |
| use_user | % |
| mysql.sys | localhost |
| root | localhost |
+-----------+-----------+
mysql>
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