mysql中创建数据表

从今天开始学习mysql数据库，希望以后能够记录自己学习的点点滴滴

mysql中创建数据表

1.创建一个数据库为test_db

mysql> create database test_db;

Query OK, 1 row affected (0.00 sec)

切换到test_db上

mysql> use test_db;

Database changed

mysql>

2.创建一个表tb_emp1

create table tb_emp1

(

 id  INT(11),

 name VARCHAR(25),

 deptid  INT (11),

 salary FLOAT

);

mysql> create table tb_emp1

    -> (

    ->  id  INT(11),

    ->  name VARCHAR(25),

    ->  deptid  INT (11),

    ->  salary FLOAT

    -> );

Query OK, 0 rows affected (0.09 sec)

 

mysql> show tables;

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

| Tables_in_test_db |

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

| tb_emp1           |

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

1 row in set (0.01 sec)

 

mysql> show create table tb_emp1 \G;

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

       Table: tb_emp1

Create Table: CREATE TABLE `tb_emp1` (

  `id` int(11) DEFAULT NULL,

  `name` varchar(25) DEFAULT NULL,

  `deptid` int(11) DEFAULT NULL,

  `salary` float DEFAULT NULL

) ENGINE=InnoDB DEFAULT CHARSET=utf8

1 row in set (0.00 sec)

 

ERROR:

No query specified

mysql>

3.使用主键约束

语法是字段名数据类型 primary key [默认值]

create table tb_emp2

(

 id  INT(11) PRIMARY KEY,

 name VARCHAR(25),

 deptid  INT (11),

 salary FLOAT

);

或者如下

create table tb_emp2

(

 id  INT(11) ,

 name VARCHAR(25),

 deptid  INT (11),

 salary FLOAT

 PRIMARY KEY (id)

);

 

mysql> create table tb_emp2

    -> (

    ->  id  INT(11) PRIMARY KEY,

    ->  name VARCHAR(25),

    ->  deptid  INT (11),

    ->  salary FLOAT

    -> );

Query OK, 0 rows affected (0.03 sec)

 

mysql> show tables;

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

| Tables_in_test_db |

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

| tb_emp1           |

| tb_emp2           |

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

2 rows in set (0.00 sec)

 

mysql> show create table tb_emp2 \G;

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

       Table: tb_emp2

Create Table: CREATE TABLE `tb_emp2` (

  `id` int(11) NOT NULL,

  `name` varchar(25) DEFAULT NULL,

  `deptid` int(11) DEFAULT NULL,

  `salary` float DEFAULT NULL,

  PRIMARY KEY (`id`)

) ENGINE=InnoDB DEFAULT CHARSET=utf8

1 row in set (0.00 sec)

ERROR:

No query specified

mysql>

 

4.表中使用外键

语法[constraint <外键名>] foreign key 字段名1 [,字段名2,…] references <主表名>

 主键列1[,主键列2,…]

主表：

create table tb_dept

(

 deptid int(11) primary key,

 name varchar(22) not null,

 location varchar(50)

)

从表：

create table tb_emp3

(

 id int(11) primary key,

 name varchar(25),

 location varchar(50),

 deptid int(11),

 salary float,

 constraint fk_emp_dept foreign key (deptid) references tb_dept (deptid)

);

 

mysql> create table tb_dept

    -> (

    ->  deptid int(11) primary key,

    ->  name varchar(22) not null,

    ->  location varchar(50)

    -> )

    -> ;

Query OK, 0 rows affected (0.05 sec)

mysql> create table tb_emp3

    -> (

    ->  id int(11) primary key,

    ->  name varchar(25),

    ->  location varchar(50),

    ->  deptid int(11),

    ->  salary float,

    ->  constraint fk_emp_dept foreign key (deptid) references tb_dept (deptid)

    -> );

Query OK, 0 rows affected (0.06 sec)

 

mysql>

 

 

mysql> show tables;

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

| Tables_in_test_db |

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

| tb_dept           |

| tb_emp1           |

| tb_emp2           |

| tb_emp3           |

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

4 rows in set (0.00 sec)

 

mysql> show create table tb_emp3 \G;

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

       Table: tb_emp3

Create Table: CREATE TABLE `tb_emp3` (

  `id` int(11) NOT NULL,

  `name` varchar(25) DEFAULT NULL,

  `location` varchar(50) DEFAULT NULL,

  `deptid` int(11) DEFAULT NULL,

  `salary` float DEFAULT NULL,

  PRIMARY KEY (`id`),

  KEY `fk_emp_dept` (`deptid`),

  CONSTRAINT `fk_emp_dept` FOREIGN KEY (`deptid`) REFERENCES `tb_dept` (`deptid`

)

) ENGINE=InnoDB DEFAULT CHARSET=utf8

1 row in set (0.00 sec)

 

ERROR:

No query specified

mysql>

 

5.表空使用非空约束(not null )和唯一约束(unique)

语法字段名数据类型 not null  , 字段名数据类型 unique

create table tb_dept1

(

 deptid int(11) primary key,

 name varchar(22) unique,

 location varchar(50) not null

);

 

mysql> create table tb_dept1

    -> (

    ->  deptid int(11) primary key,

    ->  name varchar(22) unique,

    ->  location varchar(50) not null

    -> );

Query OK, 0 rows affected (0.05 sec)

 

mysql> show create table tb_dept1 \G;

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

       Table: tb_dept1

Create Table: CREATE TABLE `tb_dept1` (

  `deptid` int(11) NOT NULL,

  `name` varchar(22) DEFAULT NULL,

  `location` varchar(50) NOT NULL,

  PRIMARY KEY (`deptid`),

  UNIQUE KEY `name` (`name`)

) ENGINE=InnoDB DEFAULT CHARSET=utf8

1 row in set (0.00 sec)

 

ERROR:

No query specified

 

6.使用默认值

语法字段名数据库类型 default

 

mysql> create table tb_emp4

    -> (

    ->  id int(11) primary key,

    ->  name varchar(25),

    ->  location varchar(50),

    ->  deptid int(11) default 1111,

    ->  salary float

    -> );

Query OK, 0 rows affected (0.05 sec)

mysql> show create table tb_emp4 \G;

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

       Table: tb_emp4

Create Table: CREATE TABLE `tb_emp4` (

  `id` int(11) NOT NULL,

  `name` varchar(25) DEFAULT NULL,

  `location` varchar(50) DEFAULT NULL,

  `deptid` int(11) DEFAULT '1111',

  `salary` float DEFAULT NULL,

  PRIMARY KEY (`id`)

) ENGINE=InnoDB DEFAULT CHARSET=utf8

1 row in set (0.00 sec)

 

ERROR:

No query specified

 

mysql>

 

7.设置表的属性字段增加（auto_increment）

mysql> create table tb_emp5

    -> (

    ->  id int(11) primary key auto_increment,

    ->  name varchar(25),

    ->  location varchar(50),

    ->  deptid int(11) default 1111,

    ->  salary float

    -> );

Query OK, 0 rows affected (0.13 sec)

 

mysql> show tables ;

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

| Tables_in_test_db |

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

| tb_dept           |

| tb_dept1          |

| tb_emp1           |

| tb_emp2           |

| tb_emp3           |

| tb_emp4           |

| tb_emp5           |

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

7 rows in set (0.00 sec)

mysql> desc tb_emp5;

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

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

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

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

| name     | varchar(25) | YES  |     | NULL    |                |

| location | varchar(50) | YES  |     | NULL    |                |

| deptid   | int(11)     | YES  |     | 1111    |                |

| salary   | float       | YES  |     | NULL    |                |

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

5 rows in set (0.00 sec)

 

mysql> show create table tb_emp5 \G;

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

       Table: tb_emp5

Create Table: CREATE TABLE `tb_emp5` (

  `id` int(11) NOT NULL AUTO_INCREMENT,

  `name` varchar(25) DEFAULT NULL,

  `location` varchar(50) DEFAULT NULL,

  `deptid` int(11) DEFAULT '1111',

  `salary` float DEFAULT NULL,

  PRIMARY KEY (`id`)

) ENGINE=InnoDB DEFAULT CHARSET=utf8

1 row in set (0.00 sec)

 

ERROR:

No query specified

 

mysql>

插入如下语句验证；

 

mysql>  insert into tb_emp5 (name,location,salary) values('ww','dd','1000'),('ja

ck','ds','3000'),('rrw','dd','1500');

Query OK, 3 rows affected (0.03 sec)

Records: 3  Duplicates: 0  Warnings: 0

 

mysql> select * from tb_emp5;

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

| id | name | location | deptid | salary |

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

|  1 | ww   | dd       |   1111 |   1000 |

|  2 | jack | ds       |   1111 |   3000 |

|  3 | rrw  | dd       |   1111 |   1500 |

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

3 rows in set (0.00 sec)

 

mysql>