Mysql怎么创建数据表

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！

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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)

Copyright (c) 2000, 2016, 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> 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;

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

| Field | Type        | Null | Key | Default | Extra |

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

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

| name  | varchar(20) | 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;

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

| Field | Type        | Null | Key | Default | Extra |

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

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

| name  | varchar(20) | YES  |     | 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;

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

| Field | Type        | Null | Key | Default | Extra |

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

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

| name  | varchar(20) | YES  |     | 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;

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

| Field | Type        | Null | Key | Default | Extra |

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

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

| name  | varchar(20) | 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;

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

| Field | Type        | Null | Key | Default | Extra |

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

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

| name  | varchar(20) | 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;

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

| Field | Type        | Null | Key | Default | Extra |

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

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

| name  | varchar(30) | YES  |     | 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;

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

| Field | Type        | Null | Key | Default | Extra |

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

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

| name  | varchar(20) | NO   |     | 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;

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

| Field | Type        | Null | Key | Default | Extra |

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

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

| name  | varchar(20) | YES  | UNI | 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;

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

| Field | Type        | Null | Key | Default | Extra          |

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

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

| name  | varchar(20) | YES  |     | NULL    |                |

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

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;

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

| Field   | Type         | Null | Key | Default | Extra          |

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

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

| name    | varchar(20)  | YES  | UNI | NULL    |                |

| address | varchar(100) | NO   |     | NULL    |                |

| city    | varchar(20)  | YES  |     | suzhou  |                |

| 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;

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

| Field | Type        | Null | Key | Default | Extra |

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

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

| name  | varchar(20) | 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)

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