mysql数据库操作

文章目录

mysql数据库操作
- 1：mysql工具使用
- 2:服务器监听的两种socket地址
- 3:mysql数据库数值类型
- 4:DDL操作
- - 4.1 数据库操作
  - 4.2：表操作
  - 4.3 用户操作
  - 4.4 查看命令show
  - 4.5 获取帮助
- 5:DML操作
- - 5.1 INSERT语句、
  - 5.2SELECT语句
  - 5.3 update语句
  - 5.4 delete语句
  - 5.5 truncate语句
- 6:dcl操作
- - 6.1 创建授权 grant
  - 6.2 查看授权
  - 6.3 取消授权revoke
  - 6.4 刷新
- 7：实战案例

1：mysql工具使用

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

2:服务器监听的两种socket地址

socket类型	说明
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

3:mysql数据库数值类型

MySQL中定义数据字段的类型对数据库的优化是非常重要的。MySQL支持多种类型，大致可以分为三类：数值、日期/时间和字符串(字符)类型。

数值类型
MySQL支持所有标准SQL数值数据类型。这些类型包括严格数值数据类型(INTEGER、SMALLINT、DECIMAL和NUMERIC)，以及近似数值数据类型(FLOAT、REAL和DOUBLE PRECISION)。

关键字INT是INTEGER的同义词，关键字DEC是DECIMAL的同义词。BIT数据类型保存位字段值，并且支持MyISAM、MEMORY、InnoDB和BDB表。作为SQL标准的扩展，MySQL也支持整数类型TINYINT、MEDIUMINT和BIGINT。下面的表显示了需要的每个整数类型的存储和范围

类型	大小	范围（有符号）	范围（无符号）	用途
tinyint	1byte	（-128,127）	（0.255）	小整数值
smallint	2bytes	（-32768.32767）	（0.65535）	大整数值
mediumint	3bytes	(-8388608,8.388607)	(0,16777215)	大整数值
int或integer	4bytes	（-2147483，2147483647）	(0,4294967295	大整数值
bigint	8bytes	(-9,223,372,036,854,775,808，9 223 372 036 854 775 807)	(0，18 446 744 073 709 551 615	极大整数值
float	4 bytes	(-3.402 823 466 E+38，-1.175 494 351 E-38)，0，(1.175 494 351 E-38，3.402 823 466 351 E+38)	0，(1.175 494 351 E-38，3.402 823 466 E+38)	单精度，浮点数值
double	8bytes	(-1.797 693 134 862 315 7 E+308，-2.225 073 858 507 201 4 E-308)，0，(2.225 073 858 507 201 4 E-308，1.797 693 134 862 315 7 E+308)	0，(2.225 073 858 507 201 4 E-308，1.797 693 134 862 315 7 E+308)	双精度浮点数值
decimal	对DECIMAL(M,D) ，如果M>D，为M+2否则为D+2	依赖于M和D的值	依赖于M和D的值	小数值

日期和时间类型
表示时间值的日期和时间类型为DATETIME、DATE、TIMESTAMP、TIME和YEAR。每个时间类型有一个有效值范围和一个"零"值，当指定不合法的MySQL不能表示的值时使用"零"值。TIMESTAMP类型有专有的自动更新特性，将在后面描述。

类型	大小（bytes）	范围	格式	用途
date	3	1000-01-01/9999-12-31	YYYY-MM-DD	日期值
time	3	‘-838:59:59’/‘838:59:59’	HH:MM:SS	时间值或持续时间
year	1	1901/2155	YYYY	年份值
datetime	8	1000-01-01 00:00:00/9999-12-31 23:59:59	YYYY-MM-DD HH:MM:SS	混合日期和时间值
timestamp	4	1970-01-01 00:00:00/2038结束时间是第 2147483647 秒，北京时间 2038-1-19 11:14:07，格林尼治时间 2038年1月19日凌晨 03:14:07	YYYYMMDD HHMMSS	混合日期和时间值，时间戳

字符串类型
字符串类型指CHAR、VARCHAR、BINARY、VARBINARY、BLOB、TEXT、ENUM和SET。该节描述了这些类型如何工作以及如何在查询中使用这些类型。

类型	大小（bytes）	用途
char	0-255	定长字符串
varchar	0-65535	变长字符串
tinyblob	0-255	不超过255个字符的二进制字符串
tinytext	0-255	短文本字符串
blob	0-65535	二进制形式的长文本数据
text	0-65535	长文本数据
mediumblob	0-16777215	二进制形式的中等长度文本数据
mediumtext	0-16777215	中等长度文本数据
longblob	0-4294967295	二进制形式的极大文本数据
longtext	0-4294967295	极大文本数据

4:DDL操作

4.1 数据库操作

创建数据库
create database 库名;


mysql> create database nian;
Query OK, 1 row affected (0.00 sec)

查看当前实例有哪些数据库
show databases;

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| nian               |
| performance_schema |
| sys                |
+--------------------+
5 rows in set (0.00 sec)

删除数据库
drop database 库名；

mysql> drop database nian;
Query OK, 0 rows affected (0.00 sec)

进入数据库
use 库名；


mysql> use nian;
Database changed

4.2：表操作

在数据库里面创建表
create table 表名（字段名1 数据类型，字段名2 数据类型）{表选项};//创建表

mysql> create table xuan(id int not null,name varchar(100) ,age tinyint);
Query OK, 0 rows affected (0.00 sec)

查看当前数据库有哪些表
show tables;

mysql> show tables;
+----------------+
| Tables_in_nian |
+----------------+
| xuan           |
+----------------+
1 row in set (0.00 sec)

删除表
drop table +表名（删除表）

mysql> drop table xuan;
Query OK, 0 rows affected (0.00 sec)

4.3 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：172.16.12.129
通配符
%：匹配任意长度的任意字符，常用于设置允许从任何主机登录
_：匹配任意单个字符

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：172.16.12.129
通配符
%：匹配任意长度的任意字符，常用于设置允许从任何主机登录
_：匹配任意单个字符

用户创建
语法：CREATE USER ‘username’@‘host’ [IDENTIFIED BY ‘password’];


mysql> create user 'xuanning'@'127.0.0.1' identified by 'xuanning@123!.Com';
Query OK, 0 rows affected (0.00 sec)

删除数据库用户
DROP USER ‘username’@‘host’;


mysql> drop user 'xuanning'@'127.0.0.1';
Query OK, 0 rows affected (0.00 sec)

4.4 查看命令show

查看支持的所有字符集
SHOW CHARACTER SET;


mysql> SHOW CHARACTER SET;
+----------+---------------------------------+---------------------+--------+
| 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 |
.......................
.......................

查看当前数据库支持的所有存储引擎
SHOW ENGINES;


mysql> SHOW ENGINES;
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| 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       |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+

查看数据库信息
SHOW DATABASES;


mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| nian               |
| performance_schema |
| sys                |
+--------------------+
5 rows in set (0.00 sec)

不进入某数据库而列出其包含的所有表
SHOW TABLES FROM 库名;


mysql> show tables from nian;
+----------------+
| Tables_in_nian |
+----------------+
| xuan           |
+----------------+
1 row in set (0.00 sec)

查看表结构
语法：DESC [db_name.]table_name;


mysql> desc nian.xuan;
+-------+---------+------+-----+---------+-------+
| Field | Type    | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+-------+
| id    | int(11) | NO   |     | NULL    |       |
| name  | int(11) | YES  |     | NULL    |       |
| age   | int(11) | YES  |     | NULL    |       |
+-------+---------+------+-----+---------+-------+
3 rows in set (0.03 sec)

查看某表的创建命令
语法：SHOW CREATE TABLE table_name;


mysql> show create table nian.xuan;
+-------+---------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table                                                                                                                                      |
+-------+---------------------------------------------------------------------------------------------------------------------------------------------------+
| xuan  | CREATE TABLE `xuan` (`id` int(11) NOT NULL,`name` int(11) DEFAULT NULL,`age` int(11) 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 'xuan'\G
*************************** 1. row ***************************Name: xuanEngine: InnoDBVersion: 10Row_format: DynamicRows: 0Avg_row_length: 0Data_length: 16384
Max_data_length: 0Index_length: 0Data_free: 0Auto_increment: NULLCreate_time: 2022-07-26 09:36:11Update_time: NULLCheck_time: NULLCollation: latin1_swedish_ciChecksum: NULLCreate_options: Comment:
1 row in set (0.00 sec)

4.5 获取帮助

获取创建表的帮助
语法：HELP keyword;

mysql> help create table;
Name: 'CREATE TABLE'
Description:
Syntax:
CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name(create_definition,...)[table_options]......
......

5:DML操作

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

5.1 INSERT语句、

DML操作之增操作insert
insert into 表名（字段名1，字段名2）values（值1，值2）（在表中插入一条数据（插入多条直接在后面加括号写值即可））
insert into 表名（字段名3，字段名5）values（值3，值5）；（值与字段名对应要插在哪里就打哪里的字段名和其对应的值）、

mysql> insert into xuan(id,name,age) values (1,'zhangsan',20);
Query OK, 1 row affected (0.00 sec)
mysql> insert into xuan(id,name) values (1,'zhangsan');
Query OK, 1 row affected (0.00 sec)
mysql> insert into xuan(id,name) values (1,'zhangsan'),(2,'zhaosi');
Query OK, 2 rows affected (0.00 sec)
Records: 2  Duplicates: 0  Warnings: 0

5.2SELECT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 IS NOT 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

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 xuan; //查看表内所有内容
+----+----------+------+
| id | name     | age  |
+----+----------+------+
|  1 | zhangsan |   20 |
|  1 | zhangsan | NULL |
|  1 | zhangsan | NULL |
|  2 | zhaosi   | NULL |
+----+----------+------+
4 rows in set (0.00 sec)mysql> select name from xuan; //查看表内name字段所有的数据
+----------+
| name     |
+----------+
| zhangsan |
| zhangsan |
| zhangsan |
| zhaosi   |
+----------+
4 rows in set (0.00 sec)mysql> select * from xuan order by age; //以age字段升序排序查询表内所有数据
+----+----------+------+
| id | name     | age  |
+----+----------+------+
|  1 | zhangsan | NULL |
|  1 | zhangsan | NULL |
|  2 | zhaosi   | NULL |
|  1 | zhangsan |   20 |
+----+----------+------+
4 rows in set (0.00 sec)mysql> select * from xuan order by age desc; //以age字段降序排序查询表内所有数据
+----+----------+------+
| id | name     | age  |
+----+----------+------+
|  1 | zhangsan |   20 |
|  1 | zhangsan | NULL |
|  1 | zhangsan | NULL |
|  2 | zhaosi   | NULL |
+----+----------+------+
4 rows in set (0.00 sec)mysql> select * from xuan order by age limit 2; //以age字段升序排序查询表内所有数据，只截取前两行
+----+----------+------+
| id | name     | age  |
+----+----------+------+
|  2 | zhaosi   | NULL |
|  1 | zhangsan | NULL |
+----+----------+------+
2 rows in set (0.00 sec)mysql> select * from xuan order by age desc limit 2;//以age字段降序排序查询表内所有数据，只截取前两行
+----+----------+------+
| id | name     | age  |
+----+----------+------+
|  1 | zhangsan |   20 |
|  1 | zhangsan | NULL |
+----+----------+------+
2 rows in set (0.00 sec)
mysql> SELECT * FROM xuan WHERE age >= 25;
+----+-----------+-------
| id | name      | age  |
+----+-----------+------+
|  3 | wangqing  |   25 |
|  4 | sean      |   28 |
|  5 | zhangshan |   26 |
+----+-----------+------+
3 rows in set (0.00 sec)mysql> SELECT * FROM xuan WHERE age >= 25 AND name = 'zhangshan';
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  5 | zhangshan |   26 |
+----+-----------+------+
1 row in set (0.00 sec)mysql> SELECT * FROM xuan WHERE age BETWEEN 23 and 28;
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  2 | jerry     |   23 |
|  3 | xuanning  |   25 |
|  4 | sean      |   28 |
|  5 | zhangshan |   26 |
+----+-----------+------+
4 rows in set (0.00 sec)mysql> select * from xuan where age is not null;
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  1 | tom       |   20 |
|  2 | jerry     |   23 |
|  3 | xuanning  |   25 |
|  4 | sean      |   28 |
|  5 | zhangshan |   26 |
|  6 | zhangshan |   20 |
+----+-----------+------+
6 rows in set (0.00 sec)mysql> select * from xuan where age is null;
+----+------+------+
| id | name | age  |
+----+------+------+
|  7 | lisi | NULL |
+----+------+------+
1 row in set (0.00 sec)

5.3 update语句

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> update xuan set age=30 where id=1; //修改id为1的数据age为30
Query OK, 3 rows affected (0.00 sec)
Rows matched: 3  Changed: 3  Warnings: 0mysql> select * from xuan;
+----+----------+------+
| id | name     | age  |
+----+----------+------+
|  1 | zhangsan |   30 |
|  1 | zhangsan |   30 |
|  1 | zhangsan |   30 |
|  2 | zhaosi   | NULL |
+----+----------+------+
4 rows in set (0.00 sec)

5.4 delete语句

语法：DELETE FROM table_name [WHERE clause] [ORDER BY ‘column_name’ [DESC]] [LIMIT [m,]n];


mysql> select * from xuan;
+----+----------+------+
| id | name     | age  |
+----+----------+------+
|  1 | zhangsan |   30 |
|  1 | zhangsan |   30 |
|  1 | zhangsan |   30 |
|  2 | zhaosi   | NULL |
|  3 | wangwu   |   21 |
|  4 | gg       |   40 |
|  5 | issi     |    7 |
+----+----------+------+
7 rows in set (0.00 sec)mysql> delete from xuan where name='issi'; //删除表内name=issi的数据
Query OK, 1 row affected (0.00 sec)mysql> select * from xuan;
+----+----------+------+
| id | name     | age  |
+----+----------+------+
|  1 | zhangsan |   30 |
|  1 | zhangsan |   30 |
|  1 | zhangsan |   30 |
|  2 | zhaosi   | NULL |
|  3 | wangwu   |   21 |
|  4 | gg       |   40 |
+----+----------+------+
6 rows in set (0.00 sec)mysql> delete from xuan;  //删除表内所有数据
Query OK, 6 rows affected (0.00 sec)mysql> select * from xuan;
Empty set (0.00 sec)

5.5 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通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

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
可以通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

语法：TRUNCATE table_name;

mysql> select * from xuan;
+----+----------+------+
| id | name     | age  |
+----+----------+------+
|  1 | zhangsan |   20 |
|  2 | zhaosi   |   30 |
|  3 | wangwu   |   40 |
|  4 | issi     |   50 |
+----+----------+------+
4 rows in set (0.00 sec)mysql> truncate xuan;
Query OK, 0 rows affected (0.01 sec)mysql> select * from xuan;
Empty set (0.00 sec)mysql> desc xuan;
+-------+--------------+------+-----+---------+-------+
| Field | Type         | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| id    | int(11)      | NO   |     | NULL    |       |
| name  | varchar(100) | YES  |     | NULL    |       |
| age   | tinyint(4)   | YES  |     | NULL    |       |
+-------+--------------+------+-----+---------+-------+
3 rows in set (0.01 sec)

6:dcl操作

6.1 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	更新内容的权限

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

语法：GRANT priv_type,… ON [object_type] db_name.table_name TO ‘username’@‘host’ [IDENTIFIED BY ‘password’] [WITH GRANT OPTION];


mysql> grant all on *.* to 'xuanning'@'localhost' identified by 'XUANning@123!'; //给予xuan用户在本机对所有库所有表有所有的权限，并设定密码为XUANning@123！
Query OK, 0 rows affected, 1 warning (0.00 sec)mysql> grant all on *.* to 'xuanning'@'%' identified by 'XUANning@123!';//给予xuan用户在所有位置上远程访问对所有库所有表有所有的权限，并设定密码为XUANning@123！
Query OK, 0 rows affected, 1 warning (0.00 sec)mysql> grant all on *.* to 'xuanning'@'127.0.0.1' identified by 'XUANning@123!';//给予xuan用户在本机对所有库所有表有所有的权限，并设定密码为XUANning@123！
Query OK, 0 rows affected, 1 warning (0.00 sec)mysql> grant all on *.* to 'xuanning'@'192.168.226.139' identified by 'XUANning@123!';  //给予xuan用户在192.168.226.139上远程访问对所有库所有表有所有的权限，并设定密码为XUANning@123！
Query OK, 0 rows affected, 1 warning (0.00 sec)

6.2 查看授权

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)

查看指定用户的授权信息


mysql> show grants for xuanning;
+-----------------------------------------------+
| Grants for xuanning@%                         |
+-----------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'xuanning'@'%' |
+-----------------------------------------------+
1 row in set (0.00 sec)

6.3 取消授权revoke

mysql> revoke all on *.* from 'xuanning'@'localhost';
Query OK, 0 rows affected (0.00 sec)mysql> revoke all on *.* from 'xuanning'@'%';
Query OK, 0 rows affected (0.00 sec)

6.4 刷新


mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)

7：实战案例

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：

mysql> desc student;
+-------+--------------+------+-----+---------+----------------+
| Field | Type         | Null | Key | Default | Extra          |
+-------+--------------+------+-----+---------+----------------+
| id    | int(11)      | NO   | PRI | NULL    | auto_increment |
| name  | varchar(100) | NO   |     | NULL    |                |
| age   | tinyint(4)   | YES  |     | NULL    |                |
+-------+--------------+------+-----+---------+----------------+3 rows in set (0.01 sec)

mysql> create database xuanning;
Query OK, 1 row affected (0.00 sec)mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| nian               |
| performance_schema |
| sys                |
| xuanning           |
+--------------------+
6 rows in set (0.00 sec)
mysql> use xuanning;
Database changed
mysql> create table student (id int not null primary key auto_increment,name varchar(100) not null,age tinyint(4));
Query OK, 0 rows affected (0.00 sec)mysql> desc student;
+-------+--------------+------+-----+---------+----------------+
| Field | Type         | Null | Key | Default | Extra          |
+-------+--------------+------+-----+---------+----------------+
| id    | int(11)      | NO   | PRI | NULL    | auto_increment |
| 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）


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：

+----+-------------+------+
| id | name        | age  |
+----+-------------+------+
|  1 | tom         |   20 |
|  2 | jerry       |   23 |
|  3 | xuanning    |   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 |
+----+-------------+------+

mysql> insert student (name,age) values ('tom',20),('jerry',23),('xuanning',25),('sean',28),('zhangshan',26),('zhangshan',20),('lisi',null),('chenshuo',10),('wangwu',3),('qiuyi',15),('qiuxiaotian',20);
Query OK, 11 rows affected (0.00 sec)
Records: 11  Duplicates: 0  Warnings: 0mysql> select * from student;
+----+-------------+------+
| id | name        | age  |
+----+-------------+------+
|  1 | tom         |   20 |
|  2 | jerry       |   23 |
|  3 | xuanning    |   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


mysql> select * from student;
+----+-------------+------+
| id | name        | age  |
+----+-------------+------+
|  1 | tom         |   20 |
|  2 | jerry       |   23 |
|  3 | xuanning    |   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)mysql> update student set age=50 where name = lisi;
ERROR 1054 (42S22): Unknown column 'lisi' in 'where clause'
mysql> update student set age=50 where name='lisi';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0mysql> select * from student;
+----+-------------+------+
| id | name        | age  |
+----+-------------+------+
|  1 | tom         |   20 |
|  2 | jerry       |   23 |
|  3 | xuanning    |   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


mysql> select * from student order by age desc;
+----+-------------+------+
| id | name        | age  |
+----+-------------+------+
|  7 | lisi        |   50 |
|  4 | sean        |   28 |
|  5 | zhangshan   |   26 |
|  3 | xuanning    |   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位同学跳过前2位

mysql> select * from student order by age limit 2,3;
+----+-------------+------+
| id | name        | age  |
+----+-------------+------+
| 10 | qiuyi       |   15 |
|  1 | tom         |   20 |
| 11 | qiuxiaotian |   20 |
+----+-------------+------+
3 rows in set (0.00 sec)

7.查询student表中年龄最大的4位同学

mysql> select * from student order by age desc limit 4;
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  7 | lisi      |   50 |
|  4 | sean      |   28 |
|  5 | zhangshan |   26 |
|  3 | xuanning  |   25 |
+----+-----------+------+
4 rows in set (0.00 sec)

8.查询student表中名字叫zhangshan的记录


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

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


mysql> select * from student where not age <23 and not age > 30;
+----+-----------+------+
| id | name      | age  |
+----+-----------+------+
|  2 | jerry     |   23 |
|  3 | xuanning  |   25 |
|  4 | sean      |   28 |
|  5 | zhangshan |   26 |
+----+-----------+------+
4 rows in set (0.00 sec)

11.修改wangwu的年龄为100

mysql> update student set age=100  where name='wangwu';
Query OK, 1 row affected (0.01 sec)
Rows matched: 1  Changed: 1  Warnings: 0mysql> select * from student where name='wangwu';
+----+--------+------+
| id | name   | age  |
+----+--------+------+
|  9 | wangwu |  100 |
+----+--------+------+
1 row 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

mysql> delete from student where name='zhangshan' and not age >20;
Query OK, 1 row affected (0.00 sec)mysql> select * from student;
+----+-------------+------+
| id | name        | age  |
+----+-------------+------+
|  1 | tom         |   20 |
|  2 | jerry       |   23 |
|  3 | xuanning    |   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)

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