Mysql怎么创建数据表

发布时间：2021-09-17 20:38:22 作者：chen
来源：亿速云阅读：249

这篇文章主要介绍“Mysql怎么创建数据表”，在日常操作中，相信很多人在Mysql怎么创建数据表问题上存在疑惑，小编查阅了各式资料，整理出简单好用的操作方法，希望对大家解答”Mysql怎么创建数据表”的疑惑有所帮助！接下来，请跟着小编一起来学习吧！

C:\Users\admin>mysql -h localhost -u root -pmysql

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 4

Server version: 5.7.14 MySQL Community Server (GPL)

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> show databases;

+--------------------+

| Database |

+--------------------+

| information_schema |

| mydata |

| mysql |

| performance_schema |

| sys |

| test |

+--------------------+

6 rows in set (0.00 sec)

mysql> use mydata

Database changed

mysql> create table mydata1(

-> id int,

-> name varchar(20),

-> sex boolean

-> );

Query OK, 0 rows affected (0.36 sec)

mysql> desc mydata1;

+-------+-------------+------+-----+---------+-------+

+-------+-------------+------+-----+---------+-------+

| id | int(11) | YES | | NULL | |

| sex | tinyint(1) | YES | | NULL | |

+-------+-------------+------+-----+---------+-------+

3 rows in set (0.02 sec)

mysql> show tables;

+------------------+

| Tables_in_mydata |

+------------------+

| mydata1 |

+------------------+

1 row in set (0.00 sec)

5.1完整性约束条件

Primary key	主键，标识唯一
Foreign key	标识该属性为该表的外键，联系表的主键
Not null	属性不能为空
Unique	属性的值是唯一的
Auto_increment	值自动增加,mysql的sql语句的特色
Default	列设置默认值

5.2 主键

单字段主键和多字段主键

mysql> create table mydata2(

-> id int primary key, #单一字段主键

-> name varchar(20),

-> sex boolean);

Query OK, 0 rows affected (0.23 sec)

mysql> show tables;

+------------------+

| Tables_in_mydata |

+------------------+

| mydata1 |

| mydata2 |

+------------------+

2 rows in set (0.00 sec)

mysql> desc mydata2;

+-------+-------------+------+-----+---------+-------+

+-------+-------------+------+-----+---------+-------+

| id | int(11) | NO | PRI | NULL | |

| sex | tinyint(1) | YES | | NULL | |

+-------+-------------+------+-----+---------+-------+

3 rows in set (0.00 sec)

mysql> alter table mydata2 drop primary key;

Query OK, 0 rows affected (0.68 sec)

Records: 0 Duplicates: 0 Warnings: 0

mysql> desc mydata2;

+-------+-------------+------+-----+---------+-------+

+-------+-------------+------+-----+---------+-------+

| id | int(11) | NO | | NULL | |

| sex | tinyint(1) | YES | | NULL | |

+-------+-------------+------+-----+---------+-------+

3 rows in set (0.00 sec)

mysql> alter table mydata2 add primary key(id,name); #设置多字段主键

Query OK, 0 rows affected (0.49 sec)

Records: 0 Duplicates: 0 Warnings: 0

mysql> desc mydata2;

+-------+-------------+------+-----+---------+-------+

+-------+-------------+------+-----+---------+-------+

| id | int(11) | NO | PRI | NULL | |

| sex | tinyint(1) | YES | | NULL | |

+-------+-------------+------+-----+---------+-------+

3 rows in set (0.00 sec)

也可以在create table 定义中定义primary key

mysql> create table mydata3(

-> id int,

-> name varchar(20),

-> sex boolean,

-> primary key(id,name)

-> );

Query OK, 0 rows affected (0.24 sec)

mysql> desc mydata3;

+-------+-------------+------+-----+---------+-------+

+-------+-------------+------+-----+---------+-------+

| id | int(11) | NO | PRI | NULL | |

| sex | tinyint(1) | YES | | NULL | |

+-------+-------------+------+-----+---------+-------+

3 rows in set (0.00 sec)

5.3 外键 foreign key

mysql> create table mydata4(

-> id int primary key,

-> name varchar(30),

-> sex boolean,

-> constraint my_fk foreign key(id) references mydata3(id)

-> );

Query OK, 0 rows affected (0.26 sec)

mysql> desc mydata4;

+-------+-------------+------+-----+---------+-------+

+-------+-------------+------+-----+---------+-------+

| id | int(11) | NO | PRI | NULL | |

| sex | tinyint(1) | YES | | NULL | |

+-------+-------------+------+-----+---------+-------+

3 rows in set (0.00 sec)

5.4 not null 非空

mysql> create table mydata5(

-> id int primary key,

-> name varchar(20) not null);

Query OK, 0 rows affected (0.28 sec)

mysql> desc mydata5;

+-------+-------------+------+-----+---------+-------+

+-------+-------------+------+-----+---------+-------+

| id | int(11) | NO | PRI | NULL | |

+-------+-------------+------+-----+---------+-------+

2 rows in set (0.00 sec)

5.5 unique 唯一性

mysql> create table mydata6(

-> id int primary key,

-> name varchar(20) unique);

Query OK, 0 rows affected (0.35 sec)

mysql> desc mydata6;

+-------+-------------+------+-----+---------+-------+

+-------+-------------+------+-----+---------+-------+

| id | int(11) | NO | PRI | NULL | |

+-------+-------------+------+-----+---------+-------+

2 rows in set (0.00 sec)

5.6 auto_increment

必须为主键的一部分

mysql> create table mydata7(

-> id int primary key auto_increment,

-> name varchar(20))

-> ;

Query OK, 0 rows affected (0.24 sec)

mysql> desc mydata7;

+-------+-------------+------+-----+---------+----------------+

+-------+-------------+------+-----+---------+----------------+

| id | int(11) | NO | PRI | NULL | auto_increment |

+-------+-------------+------+-----+---------+----------------+

2 rows in set (0.00 sec)

5.7 默认值

mysql> create table mydata8(

-> id int primary key auto_increment,

-> name varchar(20) unique,

-> address varchar(100) not null,

-> city varchar(20) default 'suzhou',

-> socre float default 0);

Query OK, 0 rows affected (0.35 sec)

mysql> desc mydata8;

+---------+--------------+------+-----+---------+----------------+

+---------+--------------+------+-----+---------+----------------+

| id | int(11) | NO | PRI | NULL | auto_increment |

| socre | float | YES | | 0 | |

+---------+--------------+------+-----+---------+----------------+

5 rows in set (0.04 sec)

5.8 查看表结构

mysql> show create table mydata1 \G;

*************************** 1. row ***************************

Table: mydata1

Create Table: CREATE TABLE `mydata1` (

`id` int(11) DEFAULT NULL,

`name` varchar(20) DEFAULT NULL,

`sex` tinyint(1) DEFAULT NULL

) ENGINE=InnoDB DEFAULT CHARSET=latin1

1 row in set (0.00 sec)

ERROR:

No query specified

mysql> desc mydata1;

+-------+-------------+------+-----+---------+-------+

+-------+-------------+------+-----+---------+-------+

| id | int(11) | YES | | NULL | |

| sex | tinyint(1) | YES | | NULL | |

+-------+-------------+------+-----+---------+-------+

3 rows in set (0.00 sec)

5.9 修改表结构

mysql> alter table mydata1 rename to mydata; #修改表名

Query OK, 0 rows affected (0.23 sec)

mysql> alter table mydata1 modify sex varchar(1); #修改列属性

Query OK, 0 rows affected (0.77 sec)

Records: 0 Duplicates: 0 Warnings: 0

mysql> alter table mydata1 change city address varchar(20);

mysql> alter table mydata1 change sex city int; #修改列名和属性

Query OK, 0 rows affected (0.94 sec)

Records: 0 Duplicates: 0 Warnings: 0

mysql> alter table mydata1 add city int; #添加列名

Query OK, 0 rows affected (0.53 sec)

Records: 0 Duplicates: 0 Warnings: 0

mysql> alter table mydata1 add sal int after address; #在address栏位后面加列

Query OK, 0 rows affected (0.35 sec)

Records: 0 Duplicates: 0 Warnings: 0

mysql> alter table mydata1 add uid int first; #加列为首列

Query OK, 0 rows affected (0.45 sec)

Records: 0 Duplicates: 0 Warnings: 0

mysql> alter table mydata1 drop city; #删除列

Query OK, 0 rows affected (0.50 sec)

Records: 0 Duplicates: 0 Warnings: 0

mysql> alter table mydata1 modify sal int after name; #修改列的位置

Query OK, 0 rows affected (0.53 sec)

Records: 0 Duplicates: 0 Warnings: 0

mysql> alter table mydata1 modify id int first; #修改为首列

Query OK, 0 rows affected (0.54 sec)

Records: 0 Duplicates: 0 Warnings: 0

CHANGE 对列进行重命名或更改列的类型，需给定旧的列名称和新的列名称、当前的类型 MODIFY 可以改变列的类型，此时不需要重命名（不需给定新的列名称）

mysql> alter table mydata1 engine=myisam; #修改表的存储引擎

Query OK, 0 rows affected (1.47 sec)

Records: 0 Duplicates: 0 Warnings: 0

mysql> drop table mydata8; #删除表

Query OK, 0 rows affected (0.22 sec)

到此，关于“Mysql怎么创建数据表”的学习就结束了，希望能够解决大家的疑惑。理论与实践的搭配能更好的帮助大家学习，快去试试吧！若想继续学习更多相关知识，请继续关注亿速云网站，小编会继续努力为大家带来更多实用的文章！

Mysql怎么创建数据表

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