mysql数据库DDL,DML,DCL操作
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: xuan
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: 2022-07-26 09:36:11
Update_time: NULL
Check_time: NULL
Collation: latin1_swedish_ci
Checksum: NULL
Create_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: 0
mysql> 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: 0
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)
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: 0
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 | 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: 0
mysql> 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)