from django.db import models# Create your models here.class Blog(models.Model):name = models.CharField(max_length=100)tagline = models.TextField()def __str__(self):return self.nameclass Author(models.Model):name = models.CharField(max_length=200)email = models.EmailField()def __str__(self):return self.nameclass Entry(models.Model):blog = models.ForeignKey(Blog, on_delete=models.CASCADE)headline = models.CharField(max_length=255)body_text = models.TextField()pub_date = models.DateField()mod_date = models.DateField()authors = models.ManyToManyField(Author)n_comments = models.IntegerField()n_pingbacks = models.IntegerField()rating = models.IntegerField()def __str__(self):return self.headline

| queryset_demo_author        |
| queryset_demo_blog          |
| queryset_demo_entry         |
| queryset_demo_entry_authors | # 在模型类中我们使用了 多对多所以系统会自动的为我们创建了一个表。
+-----------------------------+

 queryset_demo_entry_authors表结构

mysql> desc queryset_demo_entry_authors;  
+-----------+---------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------+---------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| entry_id | int(11) | NO | MUL | NULL | |
| author_id | int(11) | NO | MUL | NULL | |
+-----------+---------+------+-----+---------+----------------+
3 rows in set (0.00 sec)

(venv) lee@lee:~/PycharmProjects/Djdemo/djdemo$ python manage.py shell  # 执行shell
>>> from queryset_demo.models import Blog,Author,Entry  # 导入所需要得类
>>> b = Blog(name='Beatles Blog', tagline='All the latest Beatles news.')  # 创建对象
>>> b.save() # 存入数据库

mysql> select * from queryset_demo_blog;
+----+--------------+------------------------------+
| id | name         | tagline                      |
+----+--------------+------------------------------+
|  1 | Beatles Blog | All the latest Beatles news. |
+----+--------------+------------------------------+
1 row in set (0.01 sec)

数据库查询

>>> crete_demo = Blog.objects.create(name='create_test',tagline='This is the wayof create')
# 数据库得查询

mysql> select * from queryset_demo_blog;
+----+--------------+------------------------------+
| id | name         | tagline                      |
+----+--------------+------------------------------+
|  1 | Beatles Blog | All the latest Beatles news. |
|  2 | create_test  | This is the wayof create     |
+----+--------------+------------------------------+

create()

>>> b = Blog(name='Beatles Blog', tagline='All the latest Beatles news.')
>>> b.save()>>> b.name
'Beatles Blog'>>> b.name = 'change_new_name' # 对属性的值进行修改
>>> b.name
'change_new_name'
>>> b.save() # 将修改的值存储到数据库中

mysql> select * from queryset_demo_blog;
+----+-----------------+------------------------------+
| id | name            | tagline                      |
+----+-----------------+------------------------------+
|  1 | change_new_name | All the latest Beatles news. |
|  2 | create_test     | This is the wayof create     |
+----+-----------------+------------------------------+
2 rows in set (0.00 sec)

mysql> select * from queryset_demo_author;
+----+-------+---------------+
| id | name  | email         |
+----+-------+---------------+
|  1 | Tom   | Tom@123.com   |
|  2 | Jone  | jone@123.com  |
|  3 | Kevin | kevin@123.com |
+----+-------+---------------+
3 rows in set (0.00 sec)mysql> select * from queryset_demo_blog;
+----+-----------------+------------------------------+
| id | name            | tagline                      |
+----+-----------------+------------------------------+
|  1 | change_new_name | All the latest Beatles news. |
|  2 | create_test     | This is the wayof create     |
|  3 | Cheddar Talk    | One to Many test             |
|  4 | blog_3          | this is a test               |
+----+-----------------+------------------------------+
4 rows in set (0.00 sec)mysql> select * from queryset_demo_entry;
+----+----------+----------------+------------+------------+------------+-------------+--------+---------+
| id | headline | body_text      | pub_date   | mod_date   | n_comments | n_pingbacks | rating | blog_id |
+----+----------+----------------+------------+------------+------------+-------------+--------+---------+
|  1 | python   | This is a demo | 2018-07-11 | 2018-07-14 |         10 |          29 |     23 |       2 | # 稍后我们将进行一个修改
+----+----------+----------------+------------+------------+------------+-------------+--------+---------+
1 row in set (0.00 sec)

>>> from queryset_demo.models import Blog,Entry,Author
>>> entry = Entry.objects.get(pk=1) # 数据库中只有一条数据
>>> entry
<Entry: python> # 返回一个对象>>> entry.blog
<Blog: create_test> # 通过属性获得我们关联的一个对象>>> entry.blog.tagline
'This is the wayof create' # 获取关联对象的属性>>> change_bolg_3 = Blog.objects.get(pk=4) # 创建我们想要更新的对象>>> entry.blog = change_bolg_3
>>> entry.save()>>> entry.blog = change_bolg_3 # 跟新我们的关联
>>> entry.save() # 存储到数据库

对数据库查询验证
>>> entry = Entry.objects.get(pk=1)
>>> entry
<Entry: python>
>>> entry.blog
<Blog: blog_3>mysql> mysql> select * from queryset_demo_entry;
+----+----------+----------------+------------+------------+------------+-------------+--------+---------+
| id | headline | body_text      | pub_date   | mod_date   | n_comments | n_pingbacks | rating | blog_id |
+----+----------+----------------+------------+------------+------------+-------------+--------+---------+
|  1 | python   | This is a demo | 2018-07-11 | 2018-07-14 |         10 |          29 |     23 |       4 |
+----+----------+----------------+------------+------------+------------+-------------+--------+---------+
1 row in set (0.00 sec)

>>> john = Author.objects.create(name="John")
>>> paul = Author.objects.create(name="Paul")
>>> entry.authors.add(john,paul) # 可以同时添加多个 entry中的authors字段

数据库中进行插叙mysql> select * from queryset_demo_author;
+----+-------+---------------+
| id | name  | email         |
+----+-------+---------------+
|  1 | Tom   | Tom@123.com   |
|  2 | Jone  | jone@123.com  |
|  3 | Kevin | kevin@123.com |
|  4 | Joe   |               |
|  5 | John  |               |
|  6 | Paul  |               |
+----+-------+---------------+
6 rows in set (0.00 sec)mysql> select * from queryset_demo_entry_authors;
+----+----------+-----------+
| id | entry_id | author_id |
+----+----------+-----------+
|  1 |        1 |         2 |
|  2 |        1 |         4 |
|  3 |        1 |         5 |
|  4 |        1 |         6 |
+----+----------+-----------+
4 rows in set (0.00 sec)