mysql的小常识

为了爬虫的需要，稍微预习一下mysql；

选择当前的数据库后，查看数据库信息用：

USE;

删除：DROP DATABASE spiders

#删除name为spiders的的数据库

选择：SELECT *FROM users

 1 mysql> USE spiders;
 2 Database changed
 3 mysql> DESC users;
 4 +----------+--------------+------+-----+---------+----------------+
 5 | Field    | Type         | Null | Key | Default | Extra          |
 6 +----------+--------------+------+-----+---------+----------------+
 7 | Id       | int(11)      | NO   | PRI | NULL    | auto_increment |
 8 | email    | varchar(255) | YES  |     |         |                |
 9 | password | varchar(255) | YES  |     | NULL    |                |
10 +----------+--------------+------+-----+---------+----------------+
11 3 rows in set (0.04 sec)
12 
13 mysql> SELECT * FROM users
14     -> ;
15 +----+----------------------+-------------+
16 | Id | email                | password    |
17 +----+----------------------+-------------+
18 |  1 | webmaster@python.org | very-secret |
19 |  2 | webmaster@python.org | very-secret |
20 |  3 | webmaster@python.org | very-secret |
21 |  4 | webmaster@python.org | very-secret |
22 |  5 | webmaster@python.org | very-secret |
23 |  6 | webmaster@python.org | very-secret |
24 |  7 | webmaster@python.org | very-secret |
25 +----+----------------------+-------------+
26 7 rows in set (0.00 sec)

cha查看数据库中的表：SHOW TABLES

1 mysql> SHOW TABLES;
2 +-------------------+
3 | Tables_in_spiders |
4 +-------------------+
5 | kandong           |
6 | stu               |
7 | users             |
8 +-------------------+
9 3 rows in set (0.00 sec)

 1 mysql> ALTER TABLE kandong ADD sha INT(10);
 2 Query OK, 0 rows affected (0.27 sec)
 3 Records: 0  Duplicates: 0  Warnings: 0
 4 mysql> DESC  kandong;
 5 +-------+--------------+------+-----+---------+-------+
 6 | Field | Type         | Null | Key | Default | Extra |
 7 +-------+--------------+------+-----+---------+-------+
 8 | id    | varchar(255) | NO   | PRI | NULL    |       |
 9 | name  | varchar(255) | NO   |     | NULL    |       |
10 | age   | int(11)      | NO   |     | NULL    |       |
11 | sha   | int(10)      | YES  |     | NULL    |       |
12 +-------+--------------+------+-----+---------+-------+
13 4 rows in set (0.03 sec)