1. 关系型数据库介绍

1.1 数据结构模型

数据结构模型主要有：

  • 层次模型
  • 网状结构
  • 关系模型

关系模型： 二维关系：row，column

数据库管理系统：DBMS 关系：Relational，RDBMS

1.2 RDBMS专业名词

常见的关系型数据库管理系统：

  • MySQL：MySQL，MariaDB，Percona-Server
  • PostgreSQL：简称为pgsql
  • Oracle
  • MSSQL

记录:数据库中表的每行是一条记录

事务：多个操作被当作一个整体对待就称为一个事务

要看一个关系型数据库是否支持事务，需要看其是否支持并满足ACID测试 ACID：ACID是事务的一个基本标准

  • A：Automicity，原子性
  • C：Consistency，一致性
  • I：Isolation，隔离性
  • D：Durability，持久性

ACID，可以查看这里了解详细说明，

SQL：Structure Query Language，结构化查询语言

约束：constraint，向数据表提供的数据要遵守的限制

  • 主键约束：一个或多个字段的组合，填入的数据必须能在本表中唯一标识本行。且必须提供数据，不能为空（NOT NULL）。
  • 惟一键约束：一个或多个字段的组合，填入的数据必须能在本表中唯一标识本行。允许为空（NULL）
  • 外键约束：一个表中的某字段可填入数据取决于另一个表的主键已有的数据
  • 检查性约束

索引：将表中的一个或多个字段中的数据复制一份另存，并且这些数据需要按特定次序排序存储

关系运算：

  • 选择：挑选出符合条件的行（部分行）
  • 投影：挑选出需要的字段
  • 连接

数据抽象方式：

  • 物理层：决定数据的存储格式，即RDBMS在磁盘上如何组织文件
  • 逻辑层：描述DB存储什么数据，以及数据间存在什么样的关系
  • 视图层：描述DB中的部分数据

1.3 关系型数据库的常见组件

关系型数据库的常见组件有：

  • 数据库：database
  • 表：table，由行（row）和列（column）组成
  • 索引：index
  • 视图：view
  • 用户：user
  • 权限：privilege
  • 存储过程：procedure
  • 存储函数：function
  • 触发器：trigger
  • 事件调度器：event scheduler

1.4 SQL语句

SQL语句有三种类型：

  • DDL：Data Defination Language，数据定义语言
  • DML：Data Manipulation Language，数据操纵语言
  • DCL：Data Control Language，数据控制语言
SQL语句类型 对应操作
DDL CREATE：创建
DROP：删除
ALTER：修改
DML INSERT：向表中插入数据
DELETE：删除表中数据
UPDATE：更新表中数据
SELECT：查询表中数据
DCL GRANT：授权
REVOKE：移除授权

2. mysql安装与配置

2.1 mysql安装

mysql安装方式有三种：

  • 源代码：编译安装
  • 二进制格式的程序包：展开至特定路径，并经过简单配置后即可使用
  • 程序包管理器管理的程序包： 
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43

配置MySQL安装源:
[root@ip-10-0-100-141 ~]# cd /usr/src/
[root@ip-10-0-100-141 src]# ls
debug  kernels
[root@ip-10-0-100-141 src]# wget http://dev.mysql.com/get/mysql57-community-release-el7-10.noarch.rpm
--2019-04-22 15:04:45--  http://dev.mysql.com/get/mysql57-community-release-el7-10.noarch.rpm
正在解析主机 dev.mysql.com (dev.mysql.com)... 137.254.60.11
......

100%[=============================================>] 25,548      --.-K/s 用时 0.04s   

2019-04-22 15:04:55 (572 KB/s) - 已保存 “mysql57-community-release-el7-10.noarch.rpm” [25548/25548])

[root@ip-10-0-100-141 src]# ls
debug  kernels  mysql57-community-release-el7-10.noarch.rpm
[root@ip-10-0-100-141 src]# rpm -ivh mysql57-community-release-el7-10.noarch.rpm 
警告：mysql57-community-release-el7-10.noarch.rpm: 头V3 DSA/SHA1 Signature, 密钥 ID 5072e1f5: NOKEY
准备中...                          ################################# [100%]
正在升级/安装...
   1:mysql57-community-release-el7-10 ################################# [100%]
[root@ip-10-0-100-141 src]# ls /etc/yum.repos.d/
mysql-community.repo         redhat-rhui-client-config.repo  rhui-load-balancers.conf
mysql-community-source.repo  redhat-rhui.repo
[root@ip-10-0-100-141 src]#

安装MySQL5.7
[root@ip-10-0-100-141 ~]# yum -y install mysql-community-server mysql-community-client mysql-community-common mysql-community-devel
......
Installed:
  mysql-community-client.x86_64 0:5.7.25-1.el7                                         
  mysql-community-common.x86_64 0:5.7.25-1.el7                                         
  mysql-community-devel.x86_64 0:5.7.25-1.el7                                          
  mysql-community-libs.x86_64 0:5.7.25-1.el7                                           
  mysql-community-libs-compat.x86_64 0:5.7.25-1.el7                                    
  mysql-community-server.x86_64 0:5.7.25-1.el7                                         

Dependency Installed:
  libaio.x86_64 0:0.3.109-13.el7                                                       

Replaced:
  mariadb-libs.x86_64 1:5.5.60-1.el7_5                                                 

Complete!

2.2MySQL配置

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95

启动MySQL
[root@ip-10-0-100-141 ~]# systemctl start mysqld
[root@ip-10-0-100-141 ~]# systemctl status mysqld
● mysqld.service - MySQL Server
   Loaded: loaded (/usr/lib/systemd/system/mysqld.service; enabled; vendor preset: disabled)
   Active: active (running) since Mon 2019-04-22 07:46:26 UTC; 11s ago
     Docs: man:mysqld(8)
           http://dev.mysql.com/doc/refman/en/using-systemd.html
  Process: 4802 ExecStart=/usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid $MYSQLD_OPTS (code=exited, status=0/SUCCESS)
  Process: 4725 ExecStartPre=/usr/bin/mysqld_pre_systemd (code=exited, status=0/SUCCESS)
 Main PID: 4805 (mysqld)
   CGroup: /system.slice/mysqld.service
           └─4805 /usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid...


Apr 22 07:46:21 ip-10-0-100-141.ap-northeast-1.compute.internal systemd[1]: Starting...
Apr 22 07:46:26 ip-10-0-100-141.ap-northeast-1.compute.internal systemd[1]: Started ...
Hint: Some lines were ellipsized, use -l to show in full.

确认3306端口已经监听起来
[root@ip-10-0-100-141 ~]# ss -aultn
Netid State      Recv-Q Send-Q Local Address:Port               Peer Address:Port              
udp   UNCONN     0      0             *:68                        *:*                  
udp   UNCONN     0      0      127.0.0.1:323                       *:*                  
udp   UNCONN     0      0           ::1:323                      :::*                  
tcp   LISTEN     0      128           *:22                        *:*                  
tcp   LISTEN     0      100    127.0.0.1:25                        *:*                  
tcp   LISTEN     0      80           :::3306                     :::*                  
tcp   LISTEN     0      128          :::80                       :::*                  
tcp   LISTEN     0      128          :::22                       :::*                  
tcp   LISTEN     0      100         ::1:25                       :::*                  
tcp   LISTEN     0      128          :::443                      :::*

在日志文件中找出临时密码
[root@ip-10-0-100-141 ~]# grep password /var/log/mysqld.log 
2019-04-22T07:46:24.034205Z 1 [Note] A temporary password is generated for root@localhost: HtCqw44K),Li
[root@ip-10-0-100-141 ~]# grep password /var/log/mysqld.log |awk '{print $NF}' 
HtCqw44K),Li

使用获取到的临时密码登录MySQL
[root@ip-10-0-100-141 ~]# mysql -uroot -p'HtCqw44K),Li'
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 3
Server version: 5.7.25

Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.

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> 看到有这样的标识符则表示成功登录了
注意事项:密码有特殊字符的话,必须要用'',就像上面那样,否则不能登录


修改mysql登录密码
mysql> set global validate_password_policy=0;
Query OK, 0 rows affected (0.00 sec)

mysql> set global validate_password_length=1;
Query OK, 0 rows affected (0.00 sec)

mysql> ALTER USER 'root'@'localhost' IDENTIFIED BY 'wenhs5479!';
Query OK, 0 rows affected (0.00 sec)

mysql> quit
Bye


为避免mysql自动升级，这里需要卸载最开始安装的yum源
[root@ip-10-0-100-141 ~]# rpm -qa|grep mysql
mysql-community-libs-5.7.25-1.el7.x86_64
mysql-community-libs-compat-5.7.25-1.el7.x86_64
mysql57-community-release-el7-10.noarch
mysql-community-client-5.7.25-1.el7.x86_64
mysql-community-devel-5.7.25-1.el7.x86_64
mysql-community-common-5.7.25-1.el7.x86_64
mysql-community-server-5.7.25-1.el7.x86_64
[root@ip-10-0-100-141 ~]# yum -y remove mysql57-community-release-el7-10.noarch
Loaded plugins: amazon-id, rhui-lb, search-disabled-repos
Resolving Dependencies
--> Running transaction check
---> Package mysql57-community-release.noarch 0:el7-10 will be erased
--> Finished Dependency Resolution
......
  Erasing    : mysql57-community-release-el7-10.noarch                             1/1 
  Verifying  : mysql57-community-release-el7-10.noarch                             1/1 

Removed:
  mysql57-community-release.noarch 0:el7-10                                            

Complete!

3. mysql的程序组成

  • 客户端
  • 服务器端

3.1 mysql工具使用

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39

语法：mysql [OPTIONS] [database]
常用的OPTIONS：
    -uUSERNAME      指定用户名，默认为root
    -hHOST          指定服务器主机，默认为localhost，推荐使用ip地址
    -pPASSWORD      指定用户的密码
    -P#             指定数据库监听的端口，这里的#需用实际的端口号代替，如-P3307
    -V              查看当前使用的mysql版本
    -e          不登录mysql执行sql语句后退出，常用于脚本

[root@ip-10-0-100-141 ~]# mysql -V
mysql  Ver 14.14 Distrib 5.7.25, for Linux (x86_64) using  EditLine wrapper

[root@ip-10-0-100-141 ~]# mysql -uroot -pwenhs5479! -h127.0.0.1
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 5
Server version: 5.7.25 MySQL Community Server (GPL)

Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.

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>

注意，不推荐直接在命令行里直接用-pPASSWORD的方式登录，而是使用-p选项，然后交互式输入密码
[root@ip-10-0-100-141 ~]# mysql -uroot -p -h 127.0.0.1 -e 'SHOW DATABASES;'
Enter password: 	----->密码不会回显
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+

3.2 服务器监听的两种socket地址

socket类型

  • ip socket :默认监听在tcp的3306端口，支持远程通信
  • unix sock :监听在sock文件上（/tmp/mysql.sock，/var/lib/mysql/mysql.sock） 仅支持本地通信 server地址只能是：localhost，127.0.0.1

4.mysql数据库操作

4.1 DDL操作

4.1.1 数据库操作

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35

创建数据库
语法：CREATE DATABASE [IF NOT EXISTS] 'DB_NAME';
创建数据库wenhs
mysql> CREATE DATABASE IF NOT EXISTS wenhs;
Query OK, 1 row affected (0.00 sec)

查看当前有哪些数据库
mysql> SHOW DATABASES;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
| wenhs              |
+--------------------+
5 rows in set (0.00 sec)

删除数据库
语法：DROP DATABASE [IF EXISTS] 'DB_NAME';
删除数据库wenhs
mysql> DROP DATABASE IF EXISTS wenhs;
Query OK, 0 rows affected (0.00 sec)

mysql> SHOW DATABASES;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
4 rows in set (0.00 sec)

4.1.2 表操作

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29

创建表
语法：CREATE TABLE table_name (col1 datatype 修饰符,col2 datatype 修饰符) ENGINE='存储引擎类型';
在数据库wenhs里创建表jbgsn
mysql> CREATE DATABASE wenhs;
Query OK, 1 row affected (0.00 sec)

mysql> USE wenhs;		进入wenhs数据库
Database changed

mysql> CREATE TABLE jbgsn (id int NOT NULL,name VARCHAR(100) NOT NULL,age tinyint);
Query OK, 0 rows affected (0.02 sec)

查看当前数据库有哪些表
mysql> SHOW TABLES;
+-----------------+
| Tables_in_wenhs |
+-----------------+
| jbgsn           |
+-----------------+
1 row in set (0.00 sec)

删除表
语法：DROP TABLE [ IF EXISTS ] 'table_name';
删除表jbgsn
mysql> DROP TABLE jbgsn;
Query OK, 0 rows affected (0.00 sec)

mysql> SHOW TABLES;
Empty set (0.00 sec)

4.1.3 用户操作

mysql用户帐号由两部分组成，如'USERNAME'@'HOST'，表示此USERNAME只能从此HOST上远程登录

这里（'USERNAME'@'HOST'）的HOST用于限制此用户可通过哪些主机远程连接mysql程序，其值可为：

  • IP地址，如：10.0.100.141
  • 通配符 
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28

数据库用户创建
语法：CREATE USER 'username'@'host' [IDENTIFIED BY 'password'];
创建数据库用户wenhs
mysql> CREATE USER 'wenhs'@'127.0.0.1' IDENTIFIED BY 'wenhs5479!';
Query OK, 0 rows affected (0.00 sec)

使用新创建的用户和密码登录
[root@ip-10-0-100-141 ~]# mysql -uwenhs -pwenhs5479! -h127.0.0.1
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 9
Server version: 5.7.25 MySQL Community Server (GPL)

Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.

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>

删除数据库用户
语法：DROP USER 'username'@'host'; 
mysql> DROP USER 'wenhs'@'127.0.0.1';
Query OK, 0 rows affected (0.00 sec)
注意:自己不能删自己,所以要换root账号登录数据库

4.1.4 查看命令SHOW

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133

mysql> SHOW CHARACTER SET;			查看支持的所有字符集
+----------+---------------------------------+---------------------+--------+
| Charset  | Description                     | Default collation   | Maxlen |
+----------+---------------------------------+---------------------+--------+
| big5     | Big5 Traditional Chinese        | big5_chinese_ci     |      2 |
| dec8     | DEC West European               | dec8_swedish_ci     |      1 |
| cp850    | DOS West European               | cp850_general_ci    |      1 |
| hp8      | HP West European                | hp8_english_ci      |      1 |
| koi8r    | KOI8-R Relcom Russian           | koi8r_general_ci    |      1 |
| latin1   | cp1252 West European            | latin1_swedish_ci   |      1 |
| latin2   | ISO 8859-2 Central European     | latin2_general_ci   |      1 |
| swe7     | 7bit Swedish                    | swe7_swedish_ci     |      1 |
| ascii    | US ASCII                        | ascii_general_ci    |      1 |
| ujis     | EUC-JP Japanese                 | ujis_japanese_ci    |      3 |
| sjis     | Shift-JIS Japanese              | sjis_japanese_ci    |      2 |
| hebrew   | ISO 8859-8 Hebrew               | hebrew_general_ci   |      1 |
| tis620   | TIS620 Thai                     | tis620_thai_ci      |      1 |
| euckr    | EUC-KR Korean                   | euckr_korean_ci     |      2 |
| koi8u    | KOI8-U Ukrainian                | koi8u_general_ci    |      1 |
| gb2312   | GB2312 Simplified Chinese       | gb2312_chinese_ci   |      2 |
| greek    | ISO 8859-7 Greek                | greek_general_ci    |      1 |
| cp1250   | Windows Central European        | cp1250_general_ci   |      1 |
| gbk      | GBK Simplified Chinese          | gbk_chinese_ci      |      2 |
| latin5   | ISO 8859-9 Turkish              | latin5_turkish_ci   |      1 |
| armscii8 | ARMSCII-8 Armenian              | armscii8_general_ci |      1 |
| utf8     | UTF-8 Unicode                   | utf8_general_ci     |      3 |
| ucs2     | UCS-2 Unicode                   | ucs2_general_ci     |      2 |
| cp866    | DOS Russian                     | cp866_general_ci    |      1 |
| keybcs2  | DOS Kamenicky Czech-Slovak      | keybcs2_general_ci  |      1 |
| macce    | Mac Central European            | macce_general_ci    |      1 |
| macroman | Mac West European               | macroman_general_ci |      1 |
| cp852    | DOS Central European            | cp852_general_ci    |      1 |
| latin7   | ISO 8859-13 Baltic              | latin7_general_ci   |      1 |
| utf8mb4  | UTF-8 Unicode                   | utf8mb4_general_ci  |      4 |
| cp1251   | Windows Cyrillic                | cp1251_general_ci   |      1 |
| utf16    | UTF-16 Unicode                  | utf16_general_ci    |      4 |
| utf16le  | UTF-16LE Unicode                | utf16le_general_ci  |      4 |
| cp1256   | Windows Arabic                  | cp1256_general_ci   |      1 |
| cp1257   | Windows Baltic                  | cp1257_general_ci   |      1 |
| utf32    | UTF-32 Unicode                  | utf32_general_ci    |      4 |
| binary   | Binary pseudo charset           | binary              |      1 |
| geostd8  | GEOSTD8 Georgian                | geostd8_general_ci  |      1 |
| cp932    | SJIS for Windows Japanese       | cp932_japanese_ci   |      2 |
| eucjpms  | UJIS for Windows Japanese       | eucjpms_japanese_ci |      3 |
| gb18030  | China National Standard GB18030 | gb18030_chinese_ci  |      4 |
+----------+---------------------------------+---------------------+--------+
41 rows in set (0.00 sec)

mysql> SHOW ENGINES;			查看当前数据库支持的所有存储引擎
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| Engine             | Support | Comment                                                        | Transactions | XA   | Savepoints |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| InnoDB             | DEFAULT | Supports transactions, row-level locking, and foreign keys     | YES          | YES  | YES        |
| MRG_MYISAM         | YES     | Collection of identical MyISAM tables                          | NO           | NO   | NO         |
| MEMORY             | YES     | Hash based, stored in memory, useful for temporary tables      | NO           | NO   | NO         |
| BLACKHOLE          | YES     | /dev/null storage engine (anything you write to it disappears) | NO           | NO   | NO         |
| MyISAM             | YES     | MyISAM storage engine                                          | NO           | NO   | NO         |
| CSV                | YES     | CSV storage engine                                             | NO           | NO   | NO         |
| ARCHIVE            | YES     | Archive storage engine                                         | NO           | NO   | NO         |
| PERFORMANCE_SCHEMA | YES     | Performance Schema                                             | NO           | NO   | NO         |
| FEDERATED          | NO      | Federated MySQL storage engine                                 | NULL         | NULL | NULL       |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
9 rows in set (0.00 sec)

mysql> SHOW DATABASES;			查看数据库信息
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
| wenhs              |
+--------------------+
5 rows in set (0.00 sec)

mysql> SHOW TABLES FROM wenhs;			不进入某数据库而列出其包含的所有表
+-----------------+
| Tables_in_wenhs |
+-----------------+
| jbgsn           |
+-----------------+
1 row in set (0.00 sec)		

查看表结构
语法：DESC [db_name.]table_name;
mysql> DESC wenhs.jbgsn;
+-------+--------------+------+-----+---------+-------+
| Field | Type         | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| id    | int(11)      | NO   |     | NULL    |       |
| name  | varchar(100) | NO   |     | NULL    |       |
| age   | tinyint(4)   | YES  |     | NULL    |       |
+-------+--------------+------+-----+---------+-------+
3 rows in set (0.01 sec)

查看某表的创建命令
语法：SHOW CREATE TABLE table_name;
mysql> SHOW CREATE TABLE wenhs.jbgsn;
+-------+--------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table                                                                                                                                           |
+-------+--------------------------------------------------------------------------------------------------------------------------------------------------------+
| jbgsn | CREATE TABLE `jbgsn` (
  `id` int(11) NOT NULL,
  `name` varchar(100) NOT NULL,
  `age` tinyint(4) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1 |
+-------+--------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

查看某表的状态
语法：SHOW TABLE STATUS LIKE 'table_name'\G
mysql> SHOW TABLE STATUS LIKE 'jbgsn'\G;
*************************** 1. row ***************************
           Name: jbgsn
         Engine: InnoDB
        Version: 10
     Row_format: Dynamic
           Rows: 0
 Avg_row_length: 0
    Data_length: 16384
Max_data_length: 0
   Index_length: 0
      Data_free: 0
 Auto_increment: NULL
    Create_time: 2019-04-22 10:54:02
    Update_time: NULL
     Check_time: NULL
      Collation: latin1_swedish_ci
       Checksum: NULL
 Create_options: 
        Comment: 
1 row in set (0.00 sec)

4.1.5 获取帮助

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22

获取命令使用帮助
语法：HELP keyword;

mysql> HELP CREATE TABLE;			获取创建表的帮助
Name: 'CREATE TABLE'
Description:
Syntax:
CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
    (create_definition,...)
    [table_options]
    [partition_options]

CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
    [(create_definition,...)]
    [table_options]
    [partition_options]
    [IGNORE | REPLACE]
    [AS] query_expression

CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
    { LIKE old_tbl_name | (LIKE old_tbl_name) }
.......

4.2 DML操作

DML操作包括增(INSERT)、删(DELETE)、改(UPDATE)、查(SELECT)，均属针对表的操作。

4.2.1 INSERT语句

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37

DML操作之增操作insert
修改字段类型:alter table tb_name modify column 字段名 data_type;
语法：INSERT [INTO] table_name [(column_name,...)] {VALUES | VALUE} (value1,...),(...),...;
	INSERT INTO tb_name VALUE(value1,value2,...);	完整插入一条记录
	INSERT INTO tb_name VALUES(value1,value2,...),(value1,value2,...),...;		完整插入多条记录
	INSERT INTO tb_name(key1,key2,...) VALUE(value1,value2,...);		给指定字段插入一条记录
	INSERT INTO tb_name(key1,key2,...) VALUES(value1,value2,...),(value1,value2,...),...;		给指定字段插入多条记录
mysql> USE wenhs;
Database changed
mysql> INSERT INTO jbgsn (id,name,age) VALUE (1,'tom',20);		一次插入一条记录
Query OK, 1 row affected (0.00 sec)
mysql> INSERT INTO jbgsn (id,name,age) VALUES (2,'nbhr',23),(3,'whs',25),(4,'wen',28),(55,'ym',26),(6,'wuym',20),(7,'expl',NULL);
Query OK, 6 rows affected (0.00 sec)
Records: 6  Duplicates: 0  Warnings: 0			一次插入多条记录
mysql> INSERT INTO jbgsn(name,id) VALUES('bhg',93),('mnb',67),('jkl',85),('fg',75),('dbffd',27),('fsdf',43);
Query OK, 6 rows affected (0.01 sec)
Records: 6  Duplicates: 0  Warnings: 0

mysql> select * from jbgsn;
+----+------+------+
| id | name | age  |
+----+------+------+
|  1 | tom  |   20 |
|  2 | nbhr |   23 |
|  3 | whs  |   25 |
|  4 | wen  |   28 |
|  5 | ym   |   26 |
|  6 | wuym |   20 |
|  7 | expl | NULL |
| 93 | bhg  | NULL |
| 67 | mnb  | NULL |
| 85 | jkl  | NULL |
| 75 | fg   | NULL |
| 27 | dbfd | NULL |
| 43 | fsdf | NULL |
+----+------+------+
13 rows in set (0.00 sec)

4.2.2 SELECT语句

字段column表示法

表示符 代表什么？
* 所有字段
as 字段别名，如col1 AS alias1
当表名很长时用别名代替

条件判断语句WHERE

操作类型 常用操作符
操作符 >，<，>=，<=，=，!=
BETWEEN column# AND column#
LIKE：模糊匹配
RLIKE：基于正则表达式进行模式匹配
ISNOT NULL：非空
IS NULL：空
条件逻辑操作 AND
OR
NOT

ORDER BY：排序，默认为升序（ASC）

ORDER BY语句 意义
ORDER BY ‘column_name' 根据column_name进行升序排序
ORDER BY 'column_name' DESC 根据column_name进行降序排序
ORDER BY ’column_name' LIMIT 2 根据column_name进行升序排序
并只取前2个结果
ORDER BY ‘column_name' LIMIT 1,2 根据column_name进行升序排序
并且略过第1个结果取后面的2个结果		 
  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169

DML操作之查操作select
语法：SELECT column1,column2,... FROM table_name [WHERE clause] [ORDER BY 'column_name' [DESC]] [LIMIT [m,]n];

mysql> SELECT * FROM jbgsn;		原表情况,下列查询语句均为此表操作
+----+------+------+
| id | name | age  |
+----+------+------+
|  1 | tom  |   20 |
|  2 | nbhr |   23 |
|  3 | whs  |   25 |
|  4 | wen  |   28 |
|  5 | ym   |   26 |
|  6 | wuym |   20 |
|  7 | expl | NULL |
| 93 | bhg  | NULL |
| 67 | mnb  | NULL |
| 85 | jkl  | NULL |
| 75 | fg   | NULL |
| 27 | dbfd | NULL |
| 43 | fsdf | NULL |
+----+------+------+
13 rows in set (0.00 sec)

mysql> SELECT name,age FROM jbgsn WHERE age BETWEEN 21 AND 27;
+------+------+
| name | age  |
+------+------+
| nbhr |   23 |
| whs  |   25 |
| ym   |   26 |
+------+------+
3 rows in set (0.01 sec)

mysql> SELECT * FROM jbgsn WHERE name LIKE 'y';
Empty set (0.00 sec)

mysql> SELECT * FROM jbgsn WHERE name LIKE 'y%';
+----+------+------+
| id | name | age  |
+----+------+------+
|  5 | ym   |   26 |
+----+------+------+
1 row in set (0.00 sec)

mysql> SELECT * FROM jbgsn WHERE name LIKE 'w%';
+----+------+------+
| id | name | age  |
+----+------+------+
|  3 | whs  |   25 |
|  4 | wen  |   28 |
|  6 | wuym |   20 |
+----+------+------+
3 rows in set (0.01 sec)

mysql> SELECT * FROM jbgsn WHERE name LIKE 'w*';
Empty set (0.00 sec)

mysql> SELECT * FROM jbgsn WHERE name RLIKE 'w*';
+----+------+------+
| id | name | age  |
+----+------+------+
|  1 | tom  |   20 |
|  2 | nbhr |   23 |
|  3 | whs  |   25 |
|  4 | wen  |   28 |
|  5 | ym   |   26 |
|  6 | wuym |   20 |
|  7 | expl | NULL |
| 93 | bhg  | NULL |
| 67 | mnb  | NULL |
| 85 | jkl  | NULL |
| 75 | fg   | NULL |
| 27 | dbfd | NULL |
| 43 | fsdf | NULL |
+----+------+------+
13 rows in set (0.00 sec)

mysql> SELECT * FROM jbgsn WHERE name RLIKE 'w%';
Empty set (0.00 sec)

mysql> SELECT * FROM jbgsn WHERE age IS null;
+----+------+------+
| id | name | age  |
+----+------+------+
|  7 | expl | NULL |
| 93 | bhg  | NULL |
| 67 | mnb  | NULL |
| 85 | jkl  | NULL |
| 75 | fg   | NULL |
| 27 | dbfd | NULL |
| 43 | fsdf | NULL |
+----+------+------+
7 rows in set (0.00 sec)

mysql> SELECT * FROM jbgsn WHERE age IS NOT null;
+----+------+------+
| id | name | age  |
+----+------+------+
|  1 | tom  |   20 |
|  2 | nbhr |   23 |
|  3 | whs  |   25 |
|  4 | wen  |   28 |
|  5 | ym   |   26 |
|  6 | wuym |   20 |
+----+------+------+
6 rows in set (0.00 sec)

mysql> SELECT * FROM jbgsn ORDER BY id;		按id字段升序排序
+----+------+------+
| id | name | age  |
+----+------+------+
|  1 | tom  |   20 |
|  2 | nbhr |   23 |
|  3 | whs  |   25 |
|  4 | wen  |   28 |
|  5 | ym   |   26 |
|  6 | wuym |   20 |
|  7 | expl | NULL |
| 27 | dbfd | NULL |
| 43 | fsdf | NULL |
| 67 | mnb  | NULL |
| 75 | fg   | NULL |
| 85 | jkl  | NULL |
| 93 | bhg  | NULL |
+----+------+------+
13 rows in set (0.00 sec)

mysql> SELECT * FROM jbgsn ORDER BY id DESC;		按id字段降序排序
+----+------+------+
| id | name | age  |
+----+------+------+
| 93 | bhg  | NULL |
| 85 | jkl  | NULL |
| 75 | fg   | NULL |
| 67 | mnb  | NULL |
| 43 | fsdf | NULL |
| 27 | dbfd | NULL |
|  7 | expl | NULL |
|  6 | wuym |   20 |
|  5 | ym   |   26 |
|  4 | wen  |   28 |
|  3 | whs  |   25 |
|  2 | nbhr |   23 |
|  1 | tom  |   20 |
+----+------+------+
13 rows in set (0.00 sec)

mysql> SELECT * FROM jbgsn WHERE age IS NOT NULL ORDER BY id DESC;		取出age非空的字段并对id进行降序排序
+----+------+------+
| id | name | age  |
+----+------+------+
|  6 | wuym |   20 |
|  5 | ym   |   26 |
|  4 | wen  |   28 |
|  3 | whs  |   25 |
|  2 | nbhr |   23 |
|  1 | tom  |   20 |
+----+------+------+
6 rows in set (0.00 sec)

mysql> SELECT * FROM jbgsn WHERE age IS NOT NULL ORDER BY age DESC LIMIT 1,3;
+----+------+------+		取出age字段非空的记录并对其进行降序排序,然后跳过第一条记录,取3条记录
| id | name | age  |		order by 必须放在where语句后面
+----+------+------+
|  5 | ym   |   26 |
|  3 | whs  |   25 |
|  2 | nbhr |   23 |
+----+------+------+
3 rows in set (0.00 sec)

4.2.3 update语句

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49

DML操作之改操作update
语法：UPDATE table_name SET column1 = new_value1[,column2 = new_value2,...] [WHERE clause] [ORDER BY 'column_name' [DESC]] [LIMIT [m,]n];
mysql> select * from jbgsn;
+----+------+------+
| id | name | age  |
+----+------+------+
|  1 | tom  |   20 |
|  2 | nbhr |   23 |
|  3 | whs  |   25 |
|  4 | wen  |   28 |
|  5 | ym   |   26 |
|  6 | wuym |   20 |
|  7 | expl | NULL |
| 93 | bhg  | NULL |
| 67 | mnb  | NULL |
| 85 | jkl  | NULL |
| 75 | fg   | NULL |
| 27 | dbfd | NULL |
| 43 | fsdf | NULL |
+----+------+------+
13 rows in set (0.00 sec)

mysql> UPDATE jbgsn SET age = 88 WHERE name = 'tom';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> UPDATE jbgsn SET age = 66,id = 66  WHERE name = 'whs';
Query OK, 1 row affected (0.00 sec)		更新一条记录里面的多个字段
Rows matched: 1  Changed: 1  Warnings: 0

mysql> select * from jbgsn;
+----+------+------+
| id | name | age  |
+----+------+------+
|  1 | tom  |   88 |
|  2 | nbhr |   23 |
| 66 | whs  |   66 |
|  4 | wen  |   28 |
|  5 | ym   |   26 |
|  6 | wuym |   20 |
|  7 | expl | NULL |
| 93 | bhg  | NULL |
| 67 | mnb  | NULL |
| 85 | jkl  | NULL |
| 75 | fg   | NULL |
| 27 | dbfd | NULL |
| 43 | fsdf | NULL |
+----+------+------+
13 rows in set (0.00 sec)

4.2.4 delete语句

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47

DML操作之删操作delete
语法：DELETE FROM table_name [WHERE clause] [ORDER BY 'column_name' [DESC]] [LIMIT [m,]n];
mysql> DELETE FROM jbgsn WHERE id = 1;		删除某条记录
Query OK, 1 row affected (0.00 sec)

mysql> select * from jbgsn;
+----+------+------+
| id | name | age  |
+----+------+------+
|  2 | nbhr |   23 |
| 66 | whs  |   66 |
|  4 | wen  |   28 |
|  5 | ym   |   26 |
|  6 | wuym |   20 |
|  7 | expl | NULL |
| 93 | bhg  | NULL |
| 67 | mnb  | NULL |
| 85 | jkl  | NULL |
| 75 | fg   | NULL |
| 27 | dbfd | NULL |
| 43 | fsdf | NULL |
+----+------+------+
12 rows in set (0.00 sec)

mysql> DELETE FROM jbgsn;		删除整张表的内容
Query OK, 12 rows affected (0.00 sec)

mysql> select * from jbgsn;
Empty set (0.00 sec)

mysql> SHOW TABLES;
+-----------------+
| Tables_in_wenhs |
+-----------------+
| jbgsn           |
+-----------------+
1 row in set (0.00 sec)

mysql> DESC jbgsn;
+-------+--------------+------+-----+---------+-------+
| Field | Type         | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| id    | int(11)      | NO   |     | NULL    |       |
| name  | varchar(100) | NO   |     | NULL    |       |
| age   | tinyint(4)   | YES  |     | NULL    |       |
+-------+--------------+------+-----+---------+-------+
3 rows in set (0.00 sec)

4.2.5 truncate语句

truncate与delete的区别：

语句类型 特点
delete DELETE删除表内容时仅删除内容，但会保留表结构
DELETE语句每次删除一行，并在事务日志中为所删除的每行记录一项
可以过回滚事务日志恢复数据
非常占用空间
truncate 删除表中所有数据，且无法恢复
表结构、约束和索引等保持不变，新添加的行计数值重置为初始值
执行速度比DELETE快，且使用的系统和事务日志资源少
通过释放存储表数据所用的数据页来删除数据，并且只在事务日志中记录页的释放
对于有外键约束引用的表，不能使用TRUNCATE TABLE删除数据
不能用于加入了索引视图的表		 
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31

语法：TRUNCATE table_name;

mysql> select * from jbgsn;
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  1 | tom       |   20 |
|  2 | jerry     |   23 |
|  3 | whs       |   25 |
|  4 | shen      |   28 |
|  5 | zsdfcddan |   26 |
|  6 | adwffdsan |   20 |
|  7 | scfs      | NULL |
+----+-----------+------+
7 rows in set (0.00 sec)

mysql> truncate table jbgsn;		这个table可加可不加
Query OK, 0 rows affected (0.01 sec)

mysql> select * from jbgsn;
Empty set (0.00 sec)

mysql> DESC jbgsn;                                                                  
+-------+--------------+------+-----+---------+-------+
| Field | Type         | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| id    | int(11)      | NO   |     | NULL    |       |
| name  | varchar(100) | NO   |     | NULL    |       |
| age   | tinyint(4)   | YES  |     | NULL    |       |
+-------+--------------+------+-----+---------+-------+
3 rows in set (0.00 sec)

4.3 DCL操作

4.3.1 创建授权grant

权限类型(priv_type)

权限类型 代表什么？
ALL 所有权限
SELECT 读取内容的权限
INSERT 插入内容的权限
UPDATE 更新内容的权限
DELETE 删除内容的权限

指定要操作的对象db_name.table_name

表示方式 意义
*.* 所有库的所有表
db_name 指定库的所有表
db_name.table_name 指定库的指定表

WITH GRANT OPTION：被授权的用户可将自己的权限副本转赠给其他用户，说白点就是将自己的权限完全复制给另一个用户。不建议使用。

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27

语法:GRANT priv_type,... ON [object_type] db_name.table_name TO ‘username'@'host' [IDENTIFIED BY 'password'] [WITH GRANT OPTION];
mysql> SHOW DATABASES;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
| wenhs              |
+--------------------+
5 rows in set (0.00 sec)

授权wenhs用户在数据库本机上登录访问所有数据库
mysql> GRANT ALL ON *.* TO 'wenhs'@'localhost' IDENTIFIED BY 'WSFwdaSDFF3232?:"<>';
Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> GRANT ALL ON *.* TO 'wenhs'@'127.0.0.1' IDENTIFIED BY 'WSFwdaSDFF3232?:"<>';
Query OK, 0 rows affected, 1 warning (0.00 sec)

授权wenhs用户在10.0.100.111上远程登录访问wenhs数据库
mysql> GRANT ALL ON wenhs.* TO 'wenhs'@'10.0.100.111' IDENTIFIED BY 'WSFwdaSDFF3232?:"<>'; 
Query OK, 0 rows affected, 1 warning (0.00 sec)

授权wenhs用户在所有位置上远程登录访问wenhs数据库
mysql> GRANT ALL ON *.* TO 'wenhs'@'%' IDENTIFIED BY 'WSFwdaSDFF3232?:"<>';
Query OK, 0 rows affected, 1 warning (0.00 sec)

4.3.2 查看授权

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33

查看当前登录用户的授权信息
mysql> SHOW GRANTS;
+---------------------------------------------------------------------+
| Grants for root@localhost                                           |
+---------------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' WITH GRANT OPTION |
| GRANT PROXY ON ''@'' TO 'root'@'localhost' WITH GRANT OPTION        |
+---------------------------------------------------------------------+
2 rows in set (0.00 sec)

查看指定用户wenhs的授权信息
mysql> SHOW GRANTS FOR wenhs;
+--------------------------------------------+
| Grants for wenhs@%                         |
+--------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'wenhs'@'%' |
+--------------------------------------------+
1 row in set (0.00 sec)
mysql> SHOW GRANTS FOR 'wenhs'@'127.0.0.1';
+----------------------------------------------------+
| Grants for [email protected]                         |
+----------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'wenhs'@'127.0.0.1' |
+----------------------------------------------------+
1 row in set (0.00 sec)

mysql> SHOW GRANTS FOR 'wenhs'@'localhost';
+----------------------------------------------------+
| Grants for wenhs@localhost                         |
+----------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'wenhs'@'localhost' |
+----------------------------------------------------+
1 row in set (0.00 sec)

4.3.3 取消授权REVOKE

1
2
3
4
5
6

语法：REVOKE priv_type,... ON db_name.table_name FROM 'username'@'host';
mysql> REVOKE ALL ON *.* FROM 'wenhs'@'10.0.100.111';
Query OK, 0 rows affected (0.00 sec)

mysql> FLUSH PRIVILEGES;
Query OK, 0 rows affected (0.00 sec)

注意：mysql服务进程启动时会读取mysql库中的所有授权表至内存中：

  • GRANT或REVOKE等执行权限操作会保存于表中，mysql的服务进程会自动重读授权表，并更新至内存中
  • 对于不能够或不能及时重读授权表的命令，可手动让mysql的服务进程重读授权表
1

mysql> FLUSH PRIVILEGES;

示例

1.创建一个以你名字为名的数据库，并创建一张表student，该表包含三个字段（id，name，age），表结构如下：
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17

mysql> CREATE DATABASE IF NOT EXISTS wenhongsheng;
Query OK, 1 row affected (0.00 sec)

mysql> USE wenhongsheng;
Database changed
mysql> CREATE TABLE student (id int primary key auto_increment NOT NULL,name VARCHAR(100) NOT NULL,age tinyint);
Query OK, 0 rows affected (0.01 sec)

mysql> DESC student;
+-------+--------------+------+-----+---------+-------+
| Field | Type         | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| id    | int(11)      | NO   |     | NULL    |       |
| name  | varchar(100) | NO   |     | NULL    |       |
| age   | tinyint(4)   | YES  |     | NULL    |       |
+-------+--------------+------+-----+---------+-------+
3 rows in set (0.00 sec)
2.查看下该新建的表有无内容（用select语句）
1
2

mysql> SELECT * FROM student;
Empty set (0.00 sec)
3.往新建的student表中插入数据（用insert语句），结果应如下所示：
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22

mysql> insert into student values(1,'tom',20),(2,'jerry',23),(3,'wangqing',25),(4,'sean',28),
    -> (5,'zhangshan',26),(6,'zhangshan',20),(7,'lisi',null),(8,'chenshuo',10),(9,'wangwu',3),
    -> (10,'qiuyi',15),(11,'qiuxiaotian',20);
Query OK, 11 rows affected (0.00 sec)
Records: 11  Duplicates: 0  Warnings: 0
mysql> select * from student;     #查询表内容
+----+-------------+------+
| id | name        | age  |
+----+-------------+------+
|  1 | tom         |   20 |
|  2 | jerry       |   23 |
|  3 | wangqing    |   25 |
|  4 | sean        |   28 |
|  5 | zhangshan   |   26 |
|  6 | zhangshan   |   20 |
|  7 | lisi        | NULL |
|  8 | chenshuo    |   10 |
|  9 | wangwu      |    3 |
| 10 | qiuyi       |   15 |
| 11 | qiuxiaotian |   20 |
+----+-------------+------+
11 rows in set (0.00 sec)
4.修改lisi的年龄为50
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21

mysql> UPDATE student SET age = 50 WHERE name = 'lisi';                                        
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> SELECT * FROM student;
+----+-------------+------+
| id | name        | age  |
+----+-------------+------+
|  1 | tom         |   20 |
|  2 | jerry       |   23 |
|  3 | wangqing    |   25 |
|  4 | sean        |   28 |
|  5 | zhangshan   |   26 |
|  6 | zhangshan   |   20 |
|  7 | lisi        |   50 |
|  8 | chenshuo    |   10 |
|  9 | wangwu      |    3 |
| 10 | qiuyi       |   15 |
| 11 | qiuxiaotian |   20 |
+----+-------------+------+
11 rows in set (0.00 sec)
5.以age字段降序排序
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17

mysql> SELECT * FROM student ORDER BY age DESC;
+----+-------------+------+
| id | name        | age  |
+----+-------------+------+
|  7 | lisi        |   50 |
|  4 | sean        |   28 |
|  5 | zhangshan   |   26 |
|  3 | wangqing    |   25 |
|  2 | jerry       |   23 |
|  1 | tom         |   20 |
|  6 | zhangshan   |   20 |
| 11 | qiuxiaotian |   20 |
| 10 | qiuyi       |   15 |
|  8 | chenshuo    |   10 |
|  9 | wangwu      |    3 |
+----+-------------+------+
11 rows in set (0.00 sec)
6.查询student表中年龄最小的3位同学
1
2
3
4
5
6
7
8
9

mysql> SELECT * FROM student ORDER BY age LIMIT 3;
+----+----------+------+
| id | name     | age  |
+----+----------+------+
|  9 | wangwu   |    3 |
|  8 | chenshuo |   10 |
| 10 | qiuyi    |   15 |
+----+----------+------+
3 rows in set (0.00 sec)
7.查询student表中年龄最大的4位同学
 1
 2
 3
 4
 5
 6
 7
 8
 9
10

mysql> SELECT * FROM student ORDER BY age DESC LIMIT 4;
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  7 | lisi      |   50 |
|  4 | sean      |   28 |
|  5 | zhangshan |   26 |
|  3 | wangqing  |   25 |
+----+-----------+------+
4 rows in set (0.00 sec)
8.查询student表中名字叫zhangshan的记录
1
2
3
4
5
6
7
8

mysql> SELECT * FROM student WHERE name = 'zhangshan';
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  5 | zhangshan |   26 |
|  6 | zhangshan |   20 |
+----+-----------+------+
2 rows in set (0.00 sec)
9.查询student表中名字叫zhangshan且年龄大于20岁的记录
1
2
3
4
5
6
7

mysql> SELECT * FROM student WHERE name = 'zhangshan' AND age > 20;
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  5 | zhangshan |   26 |
+----+-----------+------+
1 row in set (0.00 sec)
10.查询student表中年龄在23到30之间的记录
1
2
3
4
5
6
7
8
9

mysql> SELECT * FROM student WHERE age BETWEEN 23 AND 30;
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  3 | wangqing  |   25 |
|  4 | sean      |   28 |
|  5 | zhangshan |   26 |
+----+-----------+------+
3 rows in set (0.00 sec)
11.修改wangwu的年龄为100
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21

mysql> UPDATE student SET age = 100 WHERE name = 'wangwu';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> SELECT * FROM student;
+----+-------------+------+
| id | name        | age  |
+----+-------------+------+
|  1 | tom         |   20 |
|  2 | jerry       |   23 |
|  3 | wangqing    |   25 |
|  4 | sean        |   28 |
|  5 | zhangshan   |   26 |
|  6 | zhangshan   |   20 |
|  7 | lisi        |   50 |
|  8 | chenshuo    |   10 |
|  9 | wangwu      |  100 |
| 10 | qiuyi       |   15 |
| 11 | qiuxiaotian |   20 |
+----+-------------+------+
11 rows in set (0.00 sec)
12.删除student中名字叫zhangshan且年龄小于等于20的记录
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19

mysql> DELETE FROM student WHERE name = 'zhangshan' AND age <= 20;
Query OK, 1 row affected (0.00 sec)

mysql> SELECT * FROM student;
+----+-------------+------+
| id | name        | age  |
+----+-------------+------+
|  1 | tom         |   20 |
|  2 | jerry       |   23 |
|  3 | wangqing    |   25 |
|  4 | sean        |   28 |
|  5 | zhangshan   |   26 |
|  7 | lisi        |   50 |
|  8 | chenshuo    |   10 |
|  9 | wangwu      |  100 |
| 10 | qiuyi       |   15 |
| 11 | qiuxiaotian |   20 |
+----+-------------+------+
10 rows in set (0.00 sec)