数据库概述、部署MySQL服务、必备命令、密码管理、安装图形软件、SELECT语法 、筛选条件

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NSD DBA DAY01

1. 案例1：构建MySQL服务器
2. 案例2：密码管理
3. 案例3：安装图形软件
4. 案例4：筛选条件

1 案例1：构建MySQL服务器

1.1 问题

1. 在IP地址192.168.88.50主机和192.168.88.51主机上部署mysql服务
2. 练习必备命令的使用

1.2 方案

准备2台虚拟机，要求如下：

表-1

 

配置yum源、关闭selinux和防火墙，如果忘记了请自行补习前边课程的知识或查看今天讲课的PPT,谢谢!!!

1.3 步骤

实现此案例需要按照如下步骤进行。

步骤一：安装软件

命令操作如下所示：

mysql-server 提供服务软件

mysql 提供命令软件

1. [root@mysql50 ~]# yum -y install mysql-server mysql //安装提供服务和命令软件
2. //软件已安装
3. [root@mysql50 ~]# rpm -q mysql-server mysql
4. mysql-server-8.0.26-1.module+el8.4.0+652+6de068a7.x86_64
5. mysql-8.0.26-1.module+el8.4.0+652+6de068a7.x86_64
6. [root@mysql50 ~]#
8. [root@mysql50 ~]# rpm -qi mysql-server //查看软件信息
9. Name : mysql-server
10. Version : 8.0.26
11. Release : 1.module+el8.4.0+652+6de068a7
12. Architecture: x86_64
13. Install Date: 2023年03月13日 星期一 12时09分38秒
14. Group : Unspecified
15. Size : 126674945
16. License : GPLv2 with exceptions and LGPLv2 and BSD
17. Signature : RSA/SHA256, 2021年09月22日 星期三 07时27分14秒, Key ID 15af5dac6d745a60
18. Source RPM : mysql-8.0.26-1.module+el8.4.0+652+6de068a7.src.rpm
19. Build Date : 2021年09月22日 星期三 07时06分32秒
20. Build Host : ord1-prod-x86build005.svc.aws.rockylinux.org
21. Relocations : (not relocatable)
22. Packager : [email protected]
23. Vendor : Rocky
24. URL : http://www.mysql.com
25. Summary : The MySQL server and related files
26. Description :
27. MySQL is a multi-user, multi-threaded SQL database server. MySQL is a
28. client/server implementation consisting of a server daemon (mysqld)
29. and many different client programs and libraries. This package contains
30. the MySQL server and some accompanying files and directories.
32. [root@mysql50 ~]# systemctl start mysqld //启动服务
33. [root@mysql50 ~]# systemctl enable mysqld //开机运行
34. [root@mysql50 ~]# systemctl enable mysqld //设置服务开机运行
35. Created symlink /etc/systemd/system/multi-user.target.wants/mysqld.service → /usr/lib/systemd/system/mysqld.service.

步骤二：查看端口号和进程名

命令操作如下所示：

1. [root@mysql50 ~]# ps -C mysqld //查看进程
2. PID TTY TIME CMD
3. 21912 ? 00:00:00 mysqld
4. [root@mysql50 ~]#
5. [root@mysql50 ~]# ss -utnlp | grep 3306 查看端口
6. tcp LISTEN 0 70 *:33060 *:* users:(("mysqld",pid=21912,fd=22))
7. tcp LISTEN 0 128 *:3306 *:* users:(("mysqld",pid=21912,fd=25))
8. [root@mysql50 ~]#
9. 或
10. [root@mysql50 ~]# netstat -utnlp | grep mysqld //仅查看mysqld进程
11. tcp6 0 0 :::33060 :::* LISTEN 21912/mysqld
12. tcp6 0 0 :::3306 :::* LISTEN 21912/mysqld
13. [root@mysql50 ~]#

说明：

MySQL 8中的3306端口是MySQL服务默认使用的端口，主要用于建立客户端与MySQL服务器之间的连接。

MySQL 8中的33060端口是MySQL Shell默认使用的管理端口，主要用于执行各种数据库管理任务。远程管理MySQL服务器：使用MySQL Shell连接到MySQL服务，并在远程管理控制台上执行各种数据库管理操作，例如创建、删除、备份和恢复数据库等。

步骤三：连接服务。

说明： 数据库管理员本机登陆默认没有密码

命令操作如下所示：

1. [root@mysql50 ~]# mysql //连接服务
2. Welcome to the MySQL monitor. Commands end with ; or \g.
3. Your MySQL connection id is 8
4. Server version: 8.0.26 Source distribution
6. Copyright (c) 2000, 2021, Oracle and/or its affiliates.
8. Oracle is a registered trademark of Oracle Corporation and/or its
9. affiliates. Other names may be trademarks of their respective
10. owners.
11. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
12. mysql> 登陆后的提示符
13. mysql> exit //断开连接
14. Bye
15. [root@mysql50 ~]#

步骤四：配置第2台数据库服务器MySQL51。

命令操作如下所示：

1. [root@mysql51 ~]# yum -y install mysql-server mysql
2. [root@mysql51 ~]# systemctl start mysqld
3. [root@mysql51 ~]# systemctl enable mysqld
4. [root@mysql51 ~]# mysql
5. mysql> exit
6. Bye
7. [root@mysql51 ~]#

步骤五：练习必备命令的使用（在mysql50主机完成练习）

命令操作如下所示：

1. mysql> select version() ; //查看数据库软件版本
2. +-----------+
3. | version() |
4. +-----------+
5. | 8.0.26 |
6. +-----------+
7. 1 row in set (0.00 sec)
9. mysql> select user() ; //查看登陆的用户和客户端地址
10. +----------------+
11. | user() |
12. +----------------+
13. | root@localhost | 管理员root本机登陆
14. +----------------+
15. 1 row in set (0.00 sec)
16. mysql> show databases; //查看已有的库
17. +--------------------+
18. | Database |
19. +--------------------+
20. | information_schema |
21. | mysql |
22. | performance_schema |
23. | sys |
24. +--------------------+
25. 4 rows in set (0.00 sec)
27. mysql>

说明：

默认4个库 不可以删除，存储的是 服务运行时加载的不同功能的程序和数据。

information_schema：是MySQL数据库提供的一个虚拟的数据库，存储了MySQL数据库中的相关信息，比如数据库、表、列、索引、权限、角色等信息。它并不存储实际的数据，而是提供了一些视图和存储过程，用于查询和管理数据库的元数据信息。

mysql：存储了MySQL服务器的系统配置、用户、账号和权限信息等。它是MySQL数据库最基本的库，存储了MySQL服务器的核心信息。

performance_schema：存储了MySQL数据库的性能指标、事件和统计信息等数据，可以用于性能分析和优化。

sys：是MySQL 8.0引入的一个新库，它基于information_schema和performance_schema视图，提供了更方便、更直观的方式来查询和管理MySQL数据库的元数据和性能数据。

1. mysql> select database(); //查看当前在那个库里 null 表示没有在任何库里
2. +------------+
3. | database() |
4. +------------+
5. | NULL |
6. +------------+
7. 1 row in set (0.00 sec)
8. mysql> use mysql ; //切换到mysql库
9. mysql> select database(); // 再次显示所在的库
10. +------------+
11. | database() |
12. +------------+
13. | mysql |
14. +------------+
15. 1 row in set (0.00 sec)
16. mysql> show tables; //显示库里已有的表
17. +------------------------------------------------------+
18. | Tables_in_mysql |
19. +------------------------------------------------------+
20. | columns_priv |
21. | component |
22. | db |
23. | default_roles |
24. | engine_cost |
25. | func |
26. | general_log |
27. | global_grants |
28. | gtid_executed |
29. | help_category |
30. | help_keyword |
31. | help_relation |
32. | help_topic |
33. | innodb_index_stats |
34. | innodb_table_stats |
35. | password_history |
36. | plugin |
37. | procs_priv |
38. | proxies_priv |
39. | replication_asynchronous_connection_failover |
40. | replication_asynchronous_connection_failover_managed |
41. | replication_group_configuration_version |
42. | replication_group_member_actions |
43. | role_edges |
44. | server_cost |
45. | servers |
46. | slave_master_info |
47. | slave_relay_log_info |
48. | slave_worker_info |
49. | slow_log |
50. | tables_priv |
51. | time_zone |
52. | time_zone_leap_second |
53. | time_zone_name |
54. | time_zone_transition |
55. | time_zone_transition_type |
56. | user |
57. +------------------------------------------------------+
58. 37 rows in set (0.00 sec)
59. mysql> exit ; 断开连接
60. Bye
61. [root@mysql50 ~]#

2 案例2：密码管理

2.1 问题

1） 在192.168.88.50主机做如下练习：

1. 设置root密码为tarena
2. 修改root密码为123qqq…A
3. 破解root密码为NSD2023…a

2.2 步骤

实现此案例需要按照如下步骤进行。

步骤一：设置root密码为tarena

命令操作如下所示：

2行输出是警告而已不用关心

1. [root@mysql50 ~]# mysqladmin -uroot -p password "tarena"
2. Enter password: //敲回车
3. mysqladmin: [Warning] Using a password on the command line interface can be insecure.
4. Warning: Since password will be sent to server in plain text, use ssl connection to ensure password safety.
5. [root@mysql50 ~]# mysql //无密码连接被拒绝
6. ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)
7. [root@mysql50 ~]#
8. [root@mysql50 ~]# mysql -uroot –ptarena //连接时输入密码
9. mysql: [Warning] Using a password on the command line interface can be insecure.
10. Welcome to the MySQL monitor. Commands end with ; or \g.
11. Your MySQL connection id is 14
12. Server version: 8.0.26 Source distribution
14. Copyright (c) 2000, 2021, Oracle and/or its affiliates.
16. Oracle is a registered trademark of Oracle Corporation and/or its
17. affiliates. Other names may be trademarks of their respective
18. owners.
20. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
22. mysql> 登陆成功

步骤二：修改root密码为123qqq…A

命令操作如下所示：

1. [root@mysql50 ~]# mysqladmin -uroot -ptarena password "123qqq...A" //修改密码
2. mysqladmin: [Warning] Using a password on the command line interface can be insecure.
3. Warning: Since password will be sent to server in plain text, use ssl connection to ensure password safety.
4. [root@mysql50 ~]# mysql -uroot –ptarena //旧密码无法登陆
5. mysql: [Warning] Using a password on the command line interface can be insecure.
6. ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES)
7. [root@mysql50 ~]# mysql -uroot -p123qqq...A //新密码登陆
8. mysql: [Warning] Using a password on the command line interface can be insecure.
9. Welcome to the MySQL monitor. Commands end with ; or \g.
10. Your MySQL connection id is 18
11. Server version: 8.0.26 Source distribution
13. Copyright (c) 2000, 2021, Oracle and/or its affiliates.
15. Oracle is a registered trademark of Oracle Corporation and/or its
16. affiliates. Other names may be trademarks of their respective
17. owners.
19. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
21. mysql> 登陆成功

步骤三：破解root密码为NSD2023…a

说明：在mysql50主机做此练习

命令操作如下所示：

1. [root@mysql50 ~]# mysql -uroot -pNSD2023...a //破解前登陆失败
2. mysql: [Warning] Using a password on the command line interface can be insecure.
3. ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES)
4. [root@mysql50 ~]# vim /etc/my.cnf.d/mysql-server.cnf //修改主配置文件
5. [mysqld]
6. skip-grant-tables //手动添加此行 作用登陆时不验证密码
7. :wq
8. [root@mysql50 ~]# systemctl restart mysqld //重启服务 作用让服务以新配置运行
9. [root@mysql50 ~]# mysql //连接服务
10. Welcome to the MySQL monitor. Commands end with ; or \g.
11. Your MySQL connection id is 7
12. Server version: 8.0.26 Source distribution
14. Copyright (c) 2000, 2021, Oracle and/or its affiliates.
16. Oracle is a registered trademark of Oracle Corporation and/or its
17. affiliates. Other names may be trademarks of their respective
18. owners.
20. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
21. //把mysql库下user表中 用户root的密码设置为无；
22. mysql> update mysql.user set authentication_string="" where user="root";
23. Query OK, 1 row affected (0.05 sec)
24. Rows matched: 1 Changed: 1 Warnings: 0
26. mysql> exit; 断开连接
27. Bye
28. [root@mysql50 ~]# vim /etc/my.cnf.d/mysql-server.cnf 编辑配置文件
29. [mysqld]
30. #skip-grant-tables //注释添加的行
31. :wq
32. [root@mysql50 ~]# systemctl restart mysqld //重启服务 作用让注释生效
33. [root@localhost ~]# mysql 无密码登陆
34. Welcome to the MySQL monitor. Commands end with ; or \g.
35. Your MySQL connection id is 8
36. Server version: 8.0.26 Source distribution
38. Copyright (c) 2000, 2021, Oracle and/or its affiliates.
40. Oracle is a registered trademark of Oracle Corporation and/or its
41. affiliates. Other names may be trademarks of their respective
42. owners.
44. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
45. //设置root用户本机登陆密码
46. mysql> alter user root@"localhost" identified by "NSD2023...a";
47. Query OK, 0 rows affected (0.00 sec)
49. mysql> exit 断开连接
50. Bye
51. [root@localhost ~]# mysql 不输密码无法登陆
52. ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)
53. [root@localhost ~]# mysql -uroot -pNSD2023...a 使用破解的密码登陆
54. mysql: [Warning] Using a password on the command line interface can be insecure.
55. Welcome to the MySQL monitor. Commands end with ; or \g.
56. Your MySQL connection id is 10
57. Server version: 8.0.26 Source distribution
58. Copyright (c) 2000, 2021, Oracle and/or its affiliates.
59. Oracle is a registered trademark of Oracle Corporation and/or its
60. affiliates. Other names may be trademarks of their respective
61. owners.
62. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
63. mysql>
64. mysql> 登陆成功
65. mysql> show databases; 查看已有的库
66. +--------------------+
67. | Database |
68. +--------------------+
69. | information_schema |
70. | mysql |
71. | performance_schema |
72. | sys |
73. +--------------------+
74. 4 rows in set (0.01 sec)

3 案例3：安装图形软件

3.1 问题

• 在IP地址192.168.88.50主机安装phpmyadmin软件
• 客户端通过访问phpmyadmin软件管理数据库

3.2 方案

把用到的软件拷贝的虚拟机mysql50里

在mysql50主机，首先配置运行环境LNP,然后安装phpmyadmin软件,最后打开真机的浏览器输入phpmyadmin的网址访问。

3.3 步骤

实现此案例需要按照如下步骤进行。

步骤一：部署运行环境LNP

命令操作如下所示：

1. gcc 源码包编译工具
2. unzip 提供解压.zip 压缩包命令
3. make 源码软件编译命令
4. pcre-devel 支持正则表达式
5. zlib-devel 提供数据压缩命令
6. [root@mysql50 ~]# yum -y install gcc unzip make pcre-devel zlib-devel //安装依赖
7. [root@mysql50 ~]# tar -xf nginx-1.22.1.tar.gz //解压源码
8. [root@mysql50 ~]# cd nginx-1.22.1 //进源码目录
9. [root@mysql50 nginx-1.22.1]# ./configure //配置
10. [root@mysql50 nginx-1.22.1]# make && make install //编译并安装
11. [root@mysql50 nginx-1.22.1]# ls /usr/local/nginx/ //查看安装目录
12. conf html logs sbin
13. [root@mysql50 nginx-1.22.1]# vim /usr/local/nginx/conf/nginx.conf //修改主配置文件
14. 43 location / {
15. 44 root html;
16. 45 index index.php index.html index.htm; //添加php首页名
17. 46 }
19. 65 location ~ \.php$ { //访问.php的请求转给本机的9000端口
20. 66 root html;
21. 67 fastcgi_pass 127.0.0.1:9000;
22. 68 fastcgi_index index.php;
23. 69 #fastcgi_param SCRIPT_FILENAME /scripts$fastcgi_script_name;
24. 70 include fastcgi.conf; //保存nginx变量文件
25. 71 }
26. :wq
27. [root@mysql50 nginx-1.22.1]# /usr/local/nginx/sbin/nginx //启动服务
28. [root@mysql50 nginx-1.22.1]# netstat -utnlp | grep 80 //查看端口
29. tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN 42182/nginx: master
30. [root@mysql50 nginx-1.22.1]#
32. php 解释php代码
33. php-devel php扩展包
34. php-mysqlnd 连接mysql命令包
35. php-json 支持json代码
36. php-fpm 提供fpm服务
37. [root@mysql50 ~]# yum -y install php php-devel php-mysqlnd php-json php-fpm //安装php软件
38. [root@mysql50 ~]# vim /etc/php-fpm.d/www.conf //修改主配置文件
39. 38 ;listen = /run/php-fpm/www.sock
40. 39 listen = 127.0.0.1:9000 //非socket方式运行,不是必须的
41. :wq
42. [root@mysql50 ~]# systemctl start php-fpm //启动服务
43. [root@mysql50 ~]# netstat -utnlp | grep 9000 //查看端口
44. tcp 0 0 127.0.0.1:9000 0.0.0.0:* LISTEN 67251/php-fpm: mast
45. [root@mysql50 ~]#
46. [root@mysql50 ~]# vim /usr/local/nginx/html/test.php //编写php脚本
48. $name = "plj" ;
49. echo $name ;
50. echo "\n" ;
51. ?>
52. :wq
53. [root@mysql50 ~]# curl http://localhost/test.php //访问脚本
54. plj
55. [root@mysql50 ~]#

步骤二：安装phpmyadmin软件

命令操作如下所示：

1. [root@mysql50 ~]# unzip phpMyAdmin-5.2.1-all-languages.zip //解压
2. [root@mysql50 ~]# mv phpMyAdmin-5.2.1-all-languages /usr/local/nginx/html/phpmyadmin //移动并改名 ，为了便于访问
3. [root@mysql50 ~]# cd /usr/local/nginx/html/phpmyadmin/ //进软件目录
4. [root@mysql50 phpmyadmin]# cp config.sample.inc.php config.inc.php //创建主配置文件
5. [root@mysql50 phpmyadmin]# vim config.inc.php //修改主配置文件
6. //定义cookies验证码
7. 16 $cfg['blowfish_secret'] = 'plj123'; /* YOU MUST FILL IN THIS FOR COOKIE AUTH! */
8. //管理本机的数据库服务
9. 30 $cfg['Servers'][$i]['host'] = 'localhost';
10. :wq
11. [root@mysql50 phpmyadmin]# setenforce 0 //关闭selinux
12. [root@mysql50 phpmyadmin]# systemctl stop firewalld //关闭防火墙

步骤三：客户端访问

命令操作如下所示：

1. http://192.168.88.50/phpmyadmin 打开浏览器输入此网址 效果如图-1所示

 

图-1

说明：输入数据库管理员root 和 密码 成功后如图-2所示

 

4 案例4：筛选条件

4.1 问题

1. 准备练习环境
2. 练习数值比较
3. 练习范围匹配
4. 练习模糊匹配
5. 练习正则匹配
6. 练习逻辑比较
7. 练习字符比较/空/非空
8. 练习别名/去重/合并

4.2 方案

拷贝tarena.sql文件到mysql50主机里，然后使用tarena.sql创建练习使用的数据。

4.3 步骤

实现此案例需要按照如下步骤进行。

步骤一：准备练习环境

1. //拷贝tarena.sql 拷贝到 mysql50主机的/root 下
2. [openeuler@server1 ~]$ scp /linux-soft/s3/tarena.sql [email protected]:/root/
3. [email protected]'s password:
4. tarena.sql 100% 284KB 171.9MB/s 00:00
5. //连接mysql50主机
6. [openeuler@server1 ~]$ ssh [email protected]
7. [email protected]'s password:
8. Last login: Tue May 23 10:59:57 2023 from 192.168.88.254
9. //恢复数据
10. [root@mysql50 ~]# mysql -uroot -pNSD2023...a < /root/tarena.sql
11. mysql: [Warning] Using a password on the command line interface can be insecure.
12. //连接服务
13. [root@mysql50 ~]# mysql -uroot -pNSD2023...a
14. mysql> show databases; //查看库
15. +--------------------+
16. | Database |
17. +--------------------+
18. | information_schema |
19. | mysql |
20. | performance_schema |
21. | sys |
22. | tarena | 恢复的库
23. +--------------------+
24. 5 rows in set (0.00 sec)
26. mysql> use tarena; //进入库
27. Reading table information for completion of table and column names
28. You can turn off this feature to get a quicker startup with -A
30. Database changed
31. mysql> show tables; //查看表
32. +------------------+
33. | Tables_in_tarena |
34. +------------------+
35. | departments | 部门表
36. | employees | 员工表
37. | salary | 工资表
38. | user | 用户表
39. +------------------+
40. 4 rows in set (0.00 sec)

使用user 表做查询练习

user表里存储的是 系统用户信息 就是 /etc/passwd 文件的内容

1. mysql> desc tarena.user; //查看表头
2. +----------+-------------+------+-----+---------+----------------+
3. | Field | Type | Null | Key | Default | Extra |
4. +----------+-------------+------+-----+---------+----------------+
5. | id | int(11) | NO | PRI | NULL | auto_increment |行号
6. | name | char(20) | YES | | NULL | |用户名
7. | password | char(1) | YES | | NULL | |密码占位符
8. | uid | int(11) | YES | | NULL | | uid号
9. | gid | int(11) | YES | | NULL | | gid号
10. | comment | varchar(50) | YES | | NULL | | 描述信息
11. | homedir | varchar(80) | YES | | NULL | | 家目录
12. | shell | char(30) | YES | | NULL | | 解释器
13. +----------+-------------+------+-----+---------+----------------+
14. 8 rows in set (0.00 sec)

select命令格式演示

语法格式1 SELECT 字段列表 FROM 库名.表名;

语法格式2 SELECT 字段列表 FROM 库名.表名 where 筛选条件;

1. mysql> select name from tarena.user;        //查看一个表头
2. mysql> select name ,uid from tarena.user;    //查看多个表头
3. mysql> select * from tarena.user;        //查看所有表头

加筛选条件

1. mysql> select * from tarena.user where name = “root”;        //查找root用户信息
2. +----+------+----------+------+------+---------+---------+-----------+
3. | id | name | password | uid | gid | comment | homedir | shell |
4. +----+------+----------+------+------+---------+---------+-----------+
5. | 1 | root | x | 0 | 0 | root | /root | /bin/bash |
6. +----+------+----------+------+------+---------+---------+-----------+
7. 1 row in set (0.00 sec)
8. mysql>
9. mysql> select * from tarena.user where id = 2 ;        //查找第2行用户信息
10. +----+------+----------+------+------+---------+---------+--------------+
11. | id | name | password | uid | gid | comment | homedir | shell |
12. +----+------+----------+------+------+---------+---------+--------------+
13. | 2 | bin | x | 1 | 1 | bin | /bin | /sbin/nologin |
14. +----+------+----------+------+------+---------+---------+--------------+
15. 1 row in set (0.00 sec)

步骤二：练习数值比较

比较符号：

= != > >= < <=

相等 不相等 大于 大于等于 小于 小于等于

符号两边要是数字或数值类型的表头 符号左边与符号右边做比较

1. //查看第3行的行号、用户名、uid、gid 四个表头的值
2. mysql> select id,name,uid,gid from tarena.user where id = 3;
3. +----+--------+------+------+
4. | id | name | uid | gid |
5. +----+--------+------+------+
6. | 3 | daemon | 2 | 2 |
7. +----+--------+------+------+
8. 1 row in set (0.00 sec)
9. //查看前2行的行号用户名、uid、gid 四个表头的值
10. mysql> select id,name,uid,gid from tarena.user where id < 3;
11. +----+------+------+------+
12. | id | name | uid | gid |
13. +----+------+------+------+
14. | 1 | root | 0 | 0 |
15. | 2 | bin | 1 | 1 |
16. +----+------+------+------+
17. 2 rows in set (0.00 sec)
19. //查看前3行的行号、用户名、uid、gid 四个表头的值
20. mysql> select id,name,uid,gid from tarena.user where id <= 3;
21. +----+--------+------+------+
22. | id | name | uid | gid |
23. +----+--------+------+------+
24. | 1 | root | 0 | 0 |
25. | 2 | bin | 1 | 1 |
26. | 3 | daemon | 2 | 2 |
27. +----+--------+------+------+
28. 3 rows in set (0.00 sec)
29. //查看前uid号大于6000的行号、用户名、uid、gid 四个表头的值
30. mysql> select id,name,uid,gid from tarena.user where uid > 6000;
31. +----+-----------+-------+-------+
32. | id | name | uid | gid |
33. +----+-----------+-------+-------+
34. | 22 | nfsnobody | 65534 | 65534 |
35. +----+-----------+-------+-------+
36. 1 row in set (0.00 sec)
37. //查看前uid号大于等于1000的行号、用户名、uid、gid 四个表头的值
38. mysql> select id,name,uid,gid from tarena.user where uid >= 1000;
39. +----+-----------+-------+-------+
40. | id | name | uid | gid |
41. +----+-----------+-------+-------+
42. | 22 | nfsnobody | 65534 | 65534 |
43. | 24 | plj | 1000 | 1000 |
44. +----+-----------+-------+-------+
45. 2 rows in set (0.00 sec)
46. //查看uid号和gid号相同的行 仅显示行号、用户名、uid、gid 四个表头的值
47. mysql> select id,name,uid,gid from tarena.user where uid = gid;
48. +----+-----------------+-------+-------+
49. | id | name | uid | gid |
50. +----+-----------------+-------+-------+
51. | 1 | root | 0 | 0 |
52. | 2 | bin | 1 | 1 |
53. | 3 | daemon | 2 | 2 |
54. | 13 | nobody | 99 | 99 |
55. | 14 | systemd-network | 192 | 192 |
56. | 15 | dbus | 81 | 81 |
57. | 17 | sshd | 74 | 74 |
58. | 18 | postfix | 89 | 89 |
59. | 20 | rpc | 32 | 32 |
60. | 21 | rpcuser | 29 | 29 |
61. | 22 | nfsnobody | 65534 | 65534 |
62. | 23 | haproxy | 188 | 188 |
63. | 24 | plj | 1000 | 1000 |
64. | 25 | apache | 48 | 48 |
65. | 26 | mysql | 27 | 27 |
66. +----+-----------------+-------+-------+
67. 15 rows in set (0.00 sec)
69. //查看uid号和gid号不一样的行 仅显示行号、用户名、uid、gid 四个表头的值
70. mysql> select id,name,uid,gid from tarena.user where uid != gid;
71. +----+----------+------+------+
72. | id | name | uid | gid |
73. +----+----------+------+------+
74. | 4 | adm | 3 | 4 |
75. | 5 | lp | 4 | 7 |
76. | 6 | sync | 5 | 0 |
77. | 7 | shutdown | 6 | 0 |
78. | 8 | halt | 7 | 0 |
79. | 9 | mail | 8 | 12 |
80. | 10 | operator | 11 | 0 |
81. | 11 | games | 12 | 100 |
82. | 12 | ftp | 14 | 50 |
83. | 16 | polkitd | 999 | 998 |
84. | 19 | chrony | 998 | 996 |
85. +----+----------+------+------+
86. 11 rows in set (0.00 sec)
87. mysql>

步骤三：练习范围匹配

in （值列表） //在…里

not in （值列表） //不在…里

between 数字1 and 数字2 //在…之间

命令操作如下所示：

1. //uid号表头的值 是 (1 , 3 , 5 , 7) 中的任意一个即可
2. mysql> select name , uid from tarena.user where uid in (1 , 3 , 5 , 7);
3. +------+------+
4. | name | uid |
5. +------+------+
6. | bin | 1 |
7. | adm | 3 |
8. | sync | 5 |
9. | halt | 7 |
10. +------+------+
11. //shell 表头的的值 不是 "/bin/bash"或"/sbin/nologin" 即可
12. mysql> select name , shell from tarena.user where shell not in ("/bin/bash","/sbin/nologin");
13. +----------+----------------+
14. | name | shell |
15. +----------+----------------+
16. | sync | /bin/sync |
17. | shutdown | /sbin/shutdown |
18. | halt | /sbin/halt |
19. | mysql | /bin/false |
20. +----------+----------------+
21. //id表头的值 在 10 到 20 之间即可 包括 10 和 20 本身
22. mysql> select id , name , uid from tarena.user where id between 10 and 20 ;
23. +----+-----------------+------+
24. | id | name | uid |
25. +----+-----------------+------+
26. | 10 | operator | 11 |
27. | 11 | games | 12 |
28. | 12 | ftp | 14 |
29. | 13 | nobody | 99 |
30. | 14 | systemd-network | 192 |
31. | 15 | dbus | 81 |
32. | 16 | polkitd | 999 |
33. | 17 | sshd | 74 |
34. | 18 | postfix | 89 |
35. | 19 | chrony | 998 |
36. | 20 | rpc | 32 |
37. +----+-----------------+------+
38. 11 rows in set (0.00 sec)mysql>

步骤四：练习模糊匹配

where 字段名 like "表达式";

通配符

_ 表示 1个字符

% 表示零个或多个字符

命令操作如下所示：

1. //找名字必须是3个字符的 （没有空格挨着敲）
2. mysql> select name from tarena.user where name like "___";
3. +------+
4. | name |
5. +------+
6. | bin |
7. | adm |
8. | ftp |
9. | rpc |
10. | plj |
11. | bob |
12. +------+
13. 6 rows in set (0.00 sec)
14. //找名字必须是4个字符的（没有空格挨着敲）
15. mysql> select name from tarena.user where name like "_ _ _ _";
16. +------+
17. | name |
18. +------+
19. | root |
20. | sync |
21. | halt |
22. | mail |
23. | dbus |
24. | sshd |
25. | null |
26. +------+
27. 7 rows in set (0.00 sec)
28. //找名字以字母a开头的（没有空格挨着敲）
29. mysql> select name from tarena.user where name like "a%";
30. //查找名字至少是4个字符的表达式
31. mysql> select name from tarena.user where name like "%_ _ _ _%";（没有空格挨着敲）
32. mysql> select name from tarena.user where name like "_ _%_ _";（没有空格挨着敲）
33. mysql> select name from tarena.user where name like "_ _ _ _%";（没有空格挨着敲）

步骤五：练习正则匹配

格式：select 字段名列表 from 库名.表名 where字段名 regexp '正则表达式'；

回顾shell课程学过的元字符(正则符号)

^ 匹配行首

$ 匹配行尾

[] 匹配范围内任意一个

* 前边的表达式出现零次或多次

| 或者

. 任意一个字符

命令操作如下所示：

1. //添加有数字的名字
2. insert into tarena.user(name)values("yaya9");
3. insert into tarena.user(name)values("6yaya");
4. insert into tarena.user(name)values("ya7ya");
5. insert into tarena.user(name)values("yay8a");
6. //查看名字里有数字的
7. mysql> select name from tarena.user where name regexp "[0-9]";
8. +-------+
9. | name |
10. +-------+
11. | yaya9 |
12. | 6yaya |
13. | ya7ya |
14. | yay8a |
15. +-------+
16. 4 rows in set (0.00 sec)
17. //查看名字以数字开头
18. mysql> select name from tarena.user where name regexp "^[0-9]";
19. +-------+
20. | name |
21. +-------+
22. | 6yaya |
23. +-------+
24. 1 row in set (0.00 sec)
25. //查看名字以数字结尾
26. mysql> select name from tarena.user where name regexp "[0-9]$";
27. +-------+
28. | name |
29. +-------+
30. | yaya9 |
31. +-------+
32. 1 row in set (0.00 sec)
33. mysql>
34. //查看名字以r开头
35. mysql> select name from tarena.user where name regexp "^r";
36. +---------+
37. | name |
38. +---------+
39. | root |
40. | rpc |
41. | rpcuser |
42. +---------+
43. 3 rows in set (0.00 sec)
44. //查看名字以t结尾
45. mysql> select name from tarena.user where name regexp "t$";
46. +------+
47. | name |
48. +------+
49. | root |
50. | halt |
51. +------+
52. 2 rows in set (0.00 sec)
53. mysql>
54. //查看名字以r开头或t结尾
55. mysql> select name from tarena.user where name regexp "^r|t$";
56. +---------+
57. | name |
58. +---------+
59. | root |
60. | halt |
61. | rpc |
62. | rpcuser |
63. +---------+
64. 4 rows in set (0.00 sec)
65. //名字r开头t结尾
66. mysql> select name from tarena.user where name regexp "^r.*t$";
67. +------+
68. | name |
69. +------+
70. | root |
71. +------+
72. 1 row in set (0.00 sec)
73. mysql>

步骤六：练习逻辑比较

多个判断条件

逻辑与 and （&&） 多个判断条件必须同时成立

逻辑或 or （||） 多个判断条件其中某个条件成立即可

逻辑非 not （!） 取反

命令操作如下所示：

1. //逻辑非例子，查看解释器不是/bin/bash 的
2. mysql> select name,shell from tarena.user where shell != "/bin/bash";
3. //not 也是取反 要放在表达式的前边
4. mysql> select name,shell from tarena.user where not shell = "/bin/bash";
5. //id值不在 10 到 20 之间
6. mysql> select id , name from tarena.user where not id between 10 and 20 ;
8. //逻辑与 例子
9. mysql> select name , uid from tarena.user where name="root" and uid = 1;
10. Empty set (0.00 sec)
11. mysql> select name , uid from tarena.user where name="root" and uid = 0;
12. +------+------+
13. | name | uid |
14. +------+------+
15. | root | 0 |
16. +------+------+
17. 1 row in set (0.00 sec)
18. //逻辑或 例子
19. mysql> select name , uid from tarena.user where name = "root" or name = "bin" or uid = 1;
20. +------+------+
21. | name | uid |
22. +------+------+
23. | root | 0 |
24. | bin | 1 |
25. +------+------+
26. mysql>

() 提高优先级

1. mysql> select 2 + 3 * 5 ; //使用默认计算顺序 先乘除后加减
2. +------------+
3. | 2 + 3 * 5 |
4. +------------+
5. | 17 |
6. +------------+
7. 1 row in set (0.00 sec)
9. mysql> select (2 + 3 ) * 5 ; //先加法再乘法
10. +---------------+
11. | (2 + 3 ) * 5 |
12. +---------------+
13. | 25 |
14. +---------------+
15. 1 row in set (0.00 sec)
17. mysql>

逻辑匹配什么时候需要加（）

逻辑与and 优先级高于逻辑或 or

如果在筛选条件里既有and 又有 or 默认先判断and 再判断or

1. //没加（） 的查询结果
2. select name , uid from tarena.user
3. where name = "root" or name = "bin" and uid = 1 ;
4. +------+------+
5. | name | uid |
6. +------+------+
7. | root | 0 |
8. | bin | 1 |
9. +------+------+
10. 2 rows in set (0.00 sec)
11. //加（）的查询结果
12. select name , uid from tarena.user
13. where (name = "root" or name = "bin") and uid = 1 ;
14. +------+------+
15. | name | uid |
16. +------+------+
17. | bin | 1 |
18. +------+------+
19. 1 row in set (0.00 sec)
20. mysql>

步骤七：练习字符比较/空/非空

符号两边必须是字符 或字符类型的表头

= 相等比较

!= 不相等比较。

命令操作如下所示：

1. //查看表里是否有名字叫apache的用户
2. mysql> select name from tarena.user where name="apache" ;
3. +--------+
4. | name |
5. +--------+
6. | apache |
7. +--------+
8. 1 row in set (0.00 sec)
9. //输出解释器不是/bin/bash的用户名 及使用的解释器
10. mysql> select name , shell from tarena.user where shell != "/bin/bash";
11. +-----------------+----------------+
12. | name | shell |
13. +-----------------+----------------+
14. | bin | /sbin/nologin |
15. | daemon | /sbin/nologin |
16. | adm | /sbin/nologin |
17. | lp | /sbin/nologin |
18. | sync | /bin/sync |
19. | shutdown | /sbin/shutdown |
20. | halt | /sbin/halt |
21. | mail | /sbin/nologin |
22. | operator | /sbin/nologin |
23. | games | /sbin/nologin |
24. | ftp | /sbin/nologin |
25. | nobody | /sbin/nologin |
26. | systemd-network | /sbin/nologin |
27. | dbus | /sbin/nologin |
28. | polkitd | /sbin/nologin |
29. | sshd | /sbin/nologin |
30. | postfix | /sbin/nologin |
31. | chrony | /sbin/nologin |
32. | rpc | /sbin/nologin |
33. | rpcuser | /sbin/nologin |
34. | nfsnobody | /sbin/nologin |
35. | haproxy | /sbin/nologin |
36. | apache | /sbin/nologin |
37. | mysql | /bin/false |
38. +-----------------+----------------+
39. 24 rows in set (0.00 sec)
40. mysql>

空 is null 表头下没有数据

非空 is not null 表头下有数据

mysql服务 使用关键字 null 或 NULL 表示表头没有数据

1. //添加新行 仅给行中的id 表头和name表头赋值
2. mysql> insert into tarena.user(id,name) values(71,""); //零个字符
3. mysql> insert into tarena.user(id,name) values(72,"null");//普通字母
4. mysql> insert into tarena.user(id,name) values(73,NULL); //表示空
5. mysql> insert into tarena.user(id,name) values(74,null); //表示空
6. //查看id表头值大于等于70 的行 仅显示行中 id表头 和 name 表头的值
7. mysql> select id , name from tarena.user where id >= 71;
8. +----+------+
9. | id | name |
10. +----+------+
11. | 71 | |
12. | 72 | null |
13. | 73 | NULL |
14. | 74 | NULL |
15. +----+------+
16. //查看name 表头没有数据的行 仅显示行中id表头 和 naeme 表头的值
17. mysql> select id , name from tarena.user where name is null;
18. +----+------+
19. | id | name |
20. +----+------+
21. | 28 | NULL |
22. | 29 | NULL |
23. | 73 | NULL |
24. | 74 | NULL |
25. +----+------+
26. //查看name 表头是0个字符的行， 仅显示行中id表头 和 naeme 表头的值
27. mysql> select id , name from tarena.user where name="";
28. +----+------+
29. | id | name |
30. +----+------+
31. | 71 | |
32. +----+------+
33. 1 row in set (0.00 sec)
34. //查看name 表头值是null的行， 仅显示行中id表头 和 naeme 表头的值
35. mysql> select id , name from tarena.user where name="null";
36. +----+------+
37. | id | name |
38. +----+------+
39. | 72 | null |
40. +----+------+
41. 1 row in set (0.00 sec)
42. //查看name 表头有数据的行， 仅显示行中id表头 和 name 表头的值
43. mysql> select id , name from tarena.user where name is not null;
44. +----+-----------------+
45. | id | name |
46. +----+-----------------+
47. | 1 | root |
48. | 2 | bin |
49. | 3 | daemon |
50. | 4 | adm |
51. | 5 | lp |
52. ....
53. ....
54. | 27 | bob |
55. | 71 | |
56. | 72 | null |
57. +----+-----------------+

步骤八：练习别名/去重/合并

命令操作如下所示：

1. //定义别名使用 as 或 空格
2. mysql> select name , homedir from tarena.user;
3. mysql> select name as 用户名 , homedir 家目录 from tarena.user;
4. //拼接 concat()
5. mysql> select concat(name,"-",uid) as 用户信息 from tarena.user where uid <= 5;
6. +--------------+
7. | 用户信息 |
8. +--------------+
9. | root-0 |
10. | bin-1 |
11. | daemon-2 |
12. | adm-3 |
13. | lp-4 |
14. | sync-5 |
15. +--------------+
16. 6 rows in set (0.00 sec)
17. //2列拼接
18. mysql> select concat(name , "-" , uid) as 用户信息 from tarena.user where uid <= 5;
19. //多列拼接
20. mysql> select concat(name , "-" , uid , "-" , gid) as 用户信息 from tarena.user where uid <= 5;
21. +--------------+
22. | 用户信息 |
23. +--------------+
24. | root-0-0 |
25. | bin-1-1 |
26. | daemon-2-2 |
27. | adm-3-4 |
28. | lp-4-7 |
29. | sync-5-0 |
30. +--------------+

去重显示 distinct 字段名列表

1. //去重前输出
2. mysql> select shell from tarena.user where shell in ("/bin/bash","/sbin/nologin") ;
3. +---------------+
4. | shell |
5. +---------------+
6. | /bin/bash |
7. | /sbin/nologin |
8. | /sbin/nologin |
9. | /sbin/nologin |
10. | /sbin/nologin |
11. | /sbin/nologin |
12. | /sbin/nologin |
13. | /sbin/nologin |
14. | /sbin/nologin |
15. | /sbin/nologin |
16. | /sbin/nologin |
17. | /sbin/nologin |
18. | /sbin/nologin |
19. | /sbin/nologin |
20. | /sbin/nologin |
21. | /sbin/nologin |
22. | /sbin/nologin |
23. | /sbin/nologin |
24. | /sbin/nologin |
25. | /sbin/nologin |
26. | /bin/bash |
27. | /sbin/nologin |
28. +---------------+
29. 22 rows in set (0.00 sec)
30. //去重后查看
31. mysql> select distinct shell from tarena.user where shell in ("/bin/bash","/sbin/nologin") ;
32. +---------------+
33. | shell |
34. +---------------+
35. | /bin/bash |
36. | /sbin/nologin |
37. +---------------+
38. 2 rows in set (0.01 sec)
39. mysql>