目录
3、使用show variables like "version"语句
知识点1：建立用户
语法形式：
root@sanchuang 10:32 mysql>help create user
Name: 'CREATE USER'
Description:
Syntax:
CREATE USER [IF NOT EXISTS]
user [auth_option] [, user [auth_option]] ...
[REQUIRE {NONE | tls_option [[AND] tls_option] ...}]
[WITH resource_option [resource_option] ...]
[password_option | lock_option] ...
示例：新建一个用户liuhongjie
root@sanchuang 10:48 mysql>create user 'liuhongjie'@'192.168.0.123' identified by 'liu123456';
Query OK, 0 rows affected (0.01 sec)
'liuhongjie' 表示新建用户名
'192.168.0.123' 表示允许用户从这台主机连接过来
identified by 设置用户密码
新建一个用户，他的用户名和密码会放到哪里？
root@sanchuang 10:52 mysql>desc mysql.user;
+------------------------+-----------------------------------+------+-----+-----------------------+-------+
| Field | Type | Null | Key | Default | Extra |
+------------------------+-----------------------------------+------+-----+-----------------------+-------+
| Host | char(60) | 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(11) unsigned | NO | | 0 | |
| max_updates | int(11) unsigned | NO | | 0 | |
| max_connections | int(11) unsigned | NO | | 0 | |
| max_user_connections | int(11) unsigned | NO | | 0 | |
| plugin | char(64) | NO | | mysql_native_password | |
| authentication_string | text | YES | | NULL | |
| password_expired | enum('N','Y') | NO | | N | |
| password_last_changed | timestamp | YES | | NULL | |
| password_lifetime | smallint(5) unsigned | YES | | NULL | |
| account_locked | enum('N','Y') | NO | | N | |
+------------------------+-----------------------------------+------+-----+-----------------------+-------+
45 rows in set (0.01 sec)
当我们新建用户的时候，create语句会别转成一条insert语句插入mysql数据库的user表里面
用户名会插入 User字段里面
主机名会插入Host字段里面
密码会插入 authentication_string字段里面
复合主键
可以看到User表里面的Host字段和User字段都是主键，也就是说名字和主机名都必须唯一，且不能为空
示例：如果我们再创建一个同名同主机名的用户就会报错
root@sanchuang 10:54 mysql>create user 'liuhongjie'@'192.168.0.123' identified by '123546'
-> ;
ERROR 1396 (HY000): Operation CREATE USER failed for 'liuhongjie'@'192.168.0.123'
但是主机名和刚才建立的liuhongjie用户不一样就可以新建成功
root@sanchuang 11:02 mysql>create user 'liuhongjie'@'192.168.0.124' identified by 'liu123456';
Query OK, 0 rows affected (0.00 sec)
查看user表里面刚才新建的字段
root@sanchuang 11:07 mysql>select user,host,authentication_string from mysql.user;
+---------------+---------------+-------------------------------------------+
| user | host | authentication_string |
+---------------+---------------+-------------------------------------------+
| root | localhost | *4ABA759CFB5DDBF29AFAFBFB03026091F6F694FD |
| mysql.session | localhost | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE |
| mysql.sys | localhost | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE |
| liming | % | *FFA025B9023C96F7DCB1078E0F171682708C9153 |
| liuhongjie | 192.168.0.123 | *0BA8D66F9147D667B15E8D10BDEB997E7E15C494 |
| liuhongjie | 192.168.0.124 | *0BA8D66F9147D667B15E8D10BDEB997E7E15C494 |
+---------------+---------------+-------------------------------------------+
6 rows in set (0.00 sec)
#######################################################
知识点2：修改用户密码：
使用 alter user 语句来修改用户密码
语法格式：
Syntax:
ALTER USER [IF EXISTS]
user [auth_option] [, user [auth_option]] ...
[REQUIRE {NONE | tls_option [[AND] tls_option] ...}]
[WITH resource_option [resource_option] ...]
[password_option | lock_option] ...
ALTER USER [IF EXISTS]
USER() IDENTIFIED BY 'auth_string'
root@sanchuang 11:07 mysql>alter user 'liuhongjie'@'192.168.0.123' identified by '123';
Query OK, 0 rows affected (0.00 sec)
#######################################################
知识点3：如何查看Mysql的版本？
1、可以在登陆Mysq的时候看到版本号
[root@localhost ~]# mysql -u root -p
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 7
Server version: 5.7.34 MySQL Community Server (GPL)
2、使用select version()语句
root@sanchuang 11:13 mysql>select version();
+-----------+
| version() |
+-----------+
| 5.7.34 |
+-----------+
1 row in set (0.00 sec)
3、使用show variables like "version"语句
root@sanchuang 11:17 mysql>show variables like "version";
+---------------+--------+
| Variable_name | Value |
+---------------+--------+
| version | 5.7.34 |
+---------------+--------+
1 row in set (0.01 sec)
#######################################################
知识点4：如何查看当前登陆用户？
root@sanchuang 11:19 mysql>select user();
+----------------+
| user() |
+----------------+
| root@localhost |
+----------------+
1 row in set (0.00 sec)
#######################################################
知识点5：如何查看当前使用的数据库？
root@sanchuang 11:21 mysql>select database();
+------------+
| database() |
+------------+
| sanchuang |
+------------+
1 row in set (0.00 sec)
#######################################################
知识点6:删除用户
示例：删除用户 [email protected]
root@sanchuang 11:21 mysql>drop user 'liuhongjie'@'192.168.0.123';
Query OK, 0 rows affected (0.00 sec)
root@sanchuang 11:34 mysql>select host,user from mysql.user;
+---------------+---------------+
| host | user |
+---------------+---------------+
| % | liming |
| 192.168.0.124 | liuhongjie |
| localhost | mysql.session |
| localhost | mysql.sys |
| localhost | root |
+---------------+---------------+
5 rows in set (0.00 sec)
root@sanchuang 11:34 mysql>
#######################################################
知识点7：Mysql默认4个数据库
root@sanchuang 11:34 mysql>show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
+--------------------+
information_schema 信息库：数据字典库
information_schema是一个信息数据库，它保存着关于Mysql服务器所维护的所有其他数据库的信息（如数据库名，数据库表，表栏的数据类型与访问权限等）
数据字典 --》元数据：描述其他数据的数据
# 查看字符集
root@sanchuang 11:51 mysql>show character set;
performance_schema 性能架构库
主要用于收集数据库服务器性能参数
执行某些操作会有性能相关的参数
sys：Mysql系统
sys库所有的数据源自performance_schema目标是把performance_schema的复杂度降低，让DBA更好的阅读这个库里面的内容，让DBA更快的了解DB的运行情况
mysql：
存放的是Mysql程序相关的表：登录用户表，时间相关表，db，权限表，mysql的核心数据库，类似于sql server中的master表，主要负责存储数据库的用户，权限设置，关键字等mysql自己需要使用的控制和管理信息。
#######################################################
知识点8：grant权限
语法格式：
Syntax:
GRANT
priv_type [(column_list)]
[, priv_type [(column_list)]] ...
ON [object_type] priv_level
TO user [auth_option] [, user [auth_option]] ...
[REQUIRE {NONE | tls_option [[AND] tls_option] ...}]
[WITH {GRANT OPTION | resource_option} ...]
GRANT PROXY ON user
TO user [, user] ...
[WITH GRANT OPTION]
示例：新建一个用户wangsh % 表示可以从任何机器连接过来
root@sanchuang 11:54 mysql>create user 'wangsh'@'%' identified by '123456';
Query OK, 0 rows affected (0.00 sec)
可以看到，普通用户只有一个默认数据库
wangsh@(none) 11:56 mysql>show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
+--------------------+
1 row in set (0.00 sec)
使用root用户给wangsh用户授权
root@sanchuang 11:59 mysql>grant select,insert on student.* to 'wangsh'@'%';
Query OK, 0 rows affected (0.00 sec)
select,insert表示给用户查询和插入语句的权利
on student.* 表示在student的所有表里面
可以看到，给wangsh用户授权对student数据库的所有表有查询，插入的权限后，wangsh用户就有student这个数据库了。
wangsh@(none) 11:56 mysql>show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| student |
+--------------------+
2 rows in set (0.00 sec)
wangsh@(none) 12:02 mysql>