2、数据库和数据库表操作

一、（dos下）数据库的创建、删除、查看和使用

1.1 普通方式登录后再使用数据库

 1 Microsoft Windows [版本 6.1.7601]
 2 版权所有 (c) 2009 Microsoft Corporation。保留所有权利。
 3
 4 C:\Users\Dell>cd c: 5
 6 c:\>d:
 7
 8 D:\>cd D:\Program Files\MySQL\MySQL Server 5.0\bin
 9
10 D:\Program Files\MySQL\MySQL Server 5.0\bin>mysql -uroot -p
11 Enter password: ****
12 Welcome to the MySQL monitor. Commands end with ; or \g.
13 Your MySQL connection id is 3
14 Server version: 5.0.45-community-nt MySQL Community Edition (GPL)
15
16 Type ‘help;‘ or ‘\h‘ for help. Type ‘\c‘ to clear the buffer.
17
18 mysql> --1.创建数据库
19 mysql> create database if not exists hollydata;
20 Query OK, 1 row affected (0.05 sec)
21
22 mysql> --2.查看数据库
23 mysql> show databases;
24 +--------------------+
25 | Database |
26 +--------------------+
27 | information_schema |
28 | hollydata |
29 | mysql |
30 | test |
31 +--------------------+
32 4 rows in set (0.00 sec)
33
34 mysql> --3.删除数据库
35 mysql> drop database if exists hollydata;
36 Query OK, 0 rows affected (0.31 sec)
37
38 mysql> --4.查看数据库
39 mysql> show databases;
40 +--------------------+
41 | Database |
42 +--------------------+
43 | information_schema |
44 | mysql |
45 | test |
46 +--------------------+
47 3 rows in set (0.00 sec)
48
49 mysql> --5.使用数据库(也就是数据的切换)
50 mysql> use test
51 Database changed
52 mysql>

数据库的创建、删除、查看、使用

1.2 在登录的时候就选择使用的数据库

登录的时候选择使用的数据库

二、结构化语言分类

三、创建数据库表语法

四、数据库列类型

4.1 数值类型

4.2 字符串类型

4.3 时间类型

4.4 null类型

五、列的属性字段

5.1 创建数据库并使用数据

1 mysql> create database hollydata;
2 Query OK, 1 row affected (0.00 sec)
3
4 mysql> use hollydata;
5 Database changed

创建数据库并使用数据

5.2 创建数据库表students

1 mysql> create table students
2     -> (id int unsigned not null auto_increment primary key,
3     ->  name char(8) not null,
4     -> sex char(4) not null,
5     -> age tinyint unsigned not null,
6     -> tel char(13) null default ‘_‘
7     -> );
8 Query OK, 0 rows affected (0.45 sec)

创建数据库表students

5.3 查看表结构

 1 mysql> desc students;
 2 +-------+---------------------+------+-----+---------+----------------+
 3 | Field | Type                | Null | Key | Default | Extra          |
 4 +-------+---------------------+------+-----+---------+----------------+
 5 | id    | int(10) unsigned    | NO   | PRI | NULL    | auto_increment |
 6 | name  | char(8)             | NO   |     |         |                |
 7 | sex   | char(4)             | NO   |     |         |                |
 8 | age   | tinyint(3) unsigned | NO   |     |         |                |
 9 | tel   | char(13)            | YES  |     | _       |                |
10 +-------+---------------------+------+-----+---------+----------------+
11 5 rows in set (0.08 sec)
12
13 mysql>

查看表结构

六、修改数据库表

6.1 修改表名

1 mysql> alter table students rename as stu;
2 Query OK, 0 rows affected (0.22 sec)

修改数据库表

6.2 查看该数据下所有的数据库表

1 mysql> show tables;
2 +---------------------+
3 | Tables_in_hollydata |
4 +---------------------+
5 | stu                 |
6 +---------------------+
7 1 row in set (0.00 sec)
8
9 mysql>

显示数据库下的所有数据库表

6.3 添加字段

 1 D:\Program Files\MySQL\MySQL Server 5.0\bin>mysql -D hollydata -u root -p
 2 Enter password: ****
 3 Welcome to the MySQL monitor.  Commands end with ; or \g.
 4 Your MySQL connection id is 6
 5 Server version: 5.0.45-community-nt MySQL Community Edition (GPL)
 6
 7 Type ‘help;‘ or ‘\h‘ for help. Type ‘\c‘ to clear the buffer.
 8
 9 mysql> --添加password密码字段
10 mysql> alter table stu add password char(8);
11 Query OK, 0 rows affected (0.32 sec)
12 Records: 0  Duplicates: 0  Warnings: 0
13
14 mysql> --查看表结构
15 mysql> desc stu;
16 +----------+---------------------+------+-----+---------+----------------+
17 | Field    | Type                | Null | Key | Default | Extra          |
18 +----------+---------------------+------+-----+---------+----------------+
19 | id       | int(10) unsigned    | NO   | PRI | NULL    | auto_increment |
20 | name     | char(8)             | NO   |     |         |                |
21 | sex      | char(4)             | NO   |     |         |                |
22 | age      | tinyint(3) unsigned | NO   |     |         |                |
23 | tel      | char(13)            | YES  |     | _       |                |
24 | password | char(8)             | YES  |     | NULL    |                |
25 +----------+---------------------+------+-----+---------+----------------+
26 6 rows in set (0.01 sec)
27
28 mysql>

添加字段

6.5 修改字段

 1 mysql> --修改password字段
 2 mysql> alter table stu modify password char(4);
 3 Query OK, 0 rows affected (0.24 sec)
 4 Records: 0  Duplicates: 0  Warnings: 0
 5
 6 mysql> alter table stu change password pwd char(5);
 7 Query OK, 0 rows affected (0.23 sec)
 8 Records: 0  Duplicates: 0  Warnings: 0
 9
10 mysql> --查看表结构
11 mysql> desc stu;
12 +-------+---------------------+------+-----+---------+----------------+
13 | Field | Type                | Null | Key | Default | Extra          |
14 +-------+---------------------+------+-----+---------+----------------+
15 | id    | int(10) unsigned    | NO   | PRI | NULL    | auto_increment |
16 | name  | char(8)             | NO   |     |         |                |
17 | sex   | char(4)             | NO   |     |         |                |
18 | age   | tinyint(3) unsigned | NO   |     |         |                |
19 | tel   | char(13)            | YES  |     | _       |                |
20 | pwd   | char(5)             | YES  |     | NULL    |                |
21 +-------+---------------------+------+-----+---------+----------------+
22 6 rows in set (0.01 sec)
23
24 mysql>

修改字段

6.6 删除字段

 1 mysql> alter table stu drop pwd;
 2 Query OK, 0 rows affected (0.24 sec)
 3 Records: 0  Duplicates: 0  Warnings: 0
 4
 5 mysql> desc stu;
 6 +-------+---------------------+------+-----+---------+----------------+
 7 | Field | Type                | Null | Key | Default | Extra          |
 8 +-------+---------------------+------+-----+---------+----------------+
 9 | id    | int(10) unsigned    | NO   | PRI | NULL    | auto_increment |
10 | name  | char(8)             | NO   |     |         |                |
11 | sex   | char(4)             | NO   |     |         |                |
12 | age   | tinyint(3) unsigned | NO   |     |         |                |
13 | tel   | char(13)            | YES  |     | _       |                |
14 +-------+---------------------+------+-----+---------+----------------+
15 5 rows in set (0.01 sec)
16
17 mysql>

删除字段

七、删除数据库表

7.1 删除数据库表

1 mysql> drop table if exists stu;
2 Query OK, 0 rows affected (0.07 sec)
3
4 mysql> --查看该库下用户下的所有数据库表
5 mysql> show tables;
6 Empty set (0.00 sec)
7
8 mysql>

删除数据库表