django数据库操作-增删改查-多对多关系以及一对多(外键)关系

django数据库操作-增删改查-多对多关系以及一对多(外键)关系

(2012-10-04 20:31:09)

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标签： 杂谈

分类：python_django

一、一对多（外键）

例子：一个作者对应多本书，一本书只有一个作者

model代码：

[python] view plain copy

1. class<wbr>Person(models.Model);<wbr><wbr></wbr></wbr></wbr>
2. name<wbr>=<wbr>models.CharField(<span style="line-height:21px; word-break:normal; word-wrap:normal">'作者姓名'</span><span style="line-height:21px; word-break:normal; word-wrap:normal">,<wbr>max_length=</wbr></span><span style="line-height:21px; word-break:normal; word-wrap:normal">10</span><span style="line-height:21px; word-break:normal; word-wrap:normal">)<wbr><wbr></wbr></wbr></span></wbr></wbr>
3. age<wbr>=<wbr>models.IntegerField(<span style="line-height:21px; word-break:normal; word-wrap:normal">'作者年龄'</span><span style="line-height:21px; word-break:normal; word-wrap:normal">)<wbr><wbr></wbr></wbr></span></wbr></wbr>
4. <wbr><wbr></wbr></wbr>
5. class<wbr>Book(models.Model):<wbr><wbr></wbr></wbr></wbr>
6. person<wbr>=<wbr>models.ForeignKey(Person,<wbr>related_name=<span style="line-height:21px; word-break:normal; word-wrap:normal">'person_book'</span><span style="line-height:21px; word-break:normal; word-wrap:normal">)<wbr><wbr></wbr></wbr></span></wbr></wbr></wbr>
7. title<wbr>=<wbr>models.CharField(<span style="line-height:21px; word-break:normal; word-wrap:normal">'书籍名称'</span><span style="line-height:21px; word-break:normal; word-wrap:normal">,<wbr>max_length=</wbr></span><span style="line-height:21px; word-break:normal; word-wrap:normal">10</span><span style="line-height:21px; word-break:normal; word-wrap:normal">)<wbr><wbr></wbr></wbr></span></wbr></wbr>
8. pubtime<wbr>=<wbr>models.DateField(<span style="line-height:21px; word-break:normal; word-wrap:normal">'出版时间'</span><span style="line-height:21px; word-break:normal; word-wrap:normal">)<wbr><wbr></wbr></wbr></span></wbr></wbr>

（一）获取对象方法：

1.从作者出发获取书籍

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1. person<wbr>=<wbr>Person.objects.fiter(你的条件)<wbr><wbr></wbr></wbr></wbr></wbr>
2. book<wbr>=<wbr>person.book_set.all()<wbr><wbr></wbr></wbr></wbr></wbr>

2.从书籍出发获取作者

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1. p<wbr>=<wbr>book.person<wbr><wbr></wbr></wbr></wbr></wbr>

二、多对多

例子：一个作者对应多本书，一本书有多个作者

model代码：

[python] view plain copy

1. class<wbr>Author(models.Model):<wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr>
2. <wbr><wbr><wbr><wbr>first_name<wbr>=<wbr>models.CharField(max_length=<span style="line-height:21px; word-break:normal; word-wrap:normal">30</span><span style="line-height:21px; word-break:normal; word-wrap:normal">)<wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></span></wbr></wbr></wbr></wbr></wbr></wbr>
3. <wbr><wbr><wbr><wbr>last_name<wbr>=<wbr>models.CharField(max_length=<span style="line-height:21px; word-break:normal; word-wrap:normal">40</span><span style="line-height:21px; word-break:normal; word-wrap:normal">)<wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></span></wbr></wbr></wbr></wbr></wbr></wbr>
4. <wbr><wbr><wbr><wbr>email<wbr>=<wbr>models.EmailField()<wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
5. <wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
6. class<wbr>Book(models.Model):<wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr>
7. <wbr><wbr><wbr><wbr>title<wbr>=<wbr>models.CharField(max_length=<span style="line-height:21px; word-break:normal; word-wrap:normal">200</span><span style="line-height:21px; word-break:normal; word-wrap:normal">)<wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></span></wbr></wbr></wbr></wbr></wbr></wbr>
8. <wbr><wbr><wbr><wbr>authors<wbr>=<wbr>models.ManyToManyField(Author)<wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

（一）获取对象方法：

1.从书籍出发获取作者

[python] view plain copy

1. b<wbr>=<wbr>Book.objects.get(id=</wbr></wbr>50)<wbr><wbr></wbr></wbr>
2. b.authors.all()<wbr><wbr></wbr></wbr>
3. b.authors.filter(first_name='Adam')<wbr><wbr></wbr></wbr>

2.从作者出发获取书籍

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1. a<wbr>=<wbr>Author.objects.get(id=</wbr></wbr>1)<wbr><wbr></wbr></wbr>
2. a.book_set.all()<wbr><wbr></wbr></wbr>

（二）添加对象方法：

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1. a<wbr>=<wbr>Author.objects.get(id=</wbr></wbr>1)<wbr><wbr></wbr></wbr>
2. b<wbr>=<wbr>Book.objects.get(id=<span style="line-height:21px; word-break:normal; word-wrap:normal">50</span><span style="line-height:21px; word-break:normal; word-wrap:normal">)<wbr><wbr></wbr></wbr></span></wbr></wbr>
3. b.authors.add(a)<wbr><wbr></wbr></wbr>

（三）删除对象对象方法：

[python] view plain copy

1. a<wbr>=<wbr>Author.objects.get(id=</wbr></wbr>1)<wbr><wbr></wbr></wbr>
2. b<wbr>=<wbr>Book.objects.get(id=<span style="line-height:21px; word-break:normal; word-wrap:normal">50</span><span style="line-height:21px; word-break:normal; word-wrap:normal">)<wbr><wbr></wbr></wbr></span></wbr></wbr>
3. b.authors.remove(a)<wbr>或者<wbr>b.authors.filter(id=<span style="line-height:21px; word-break:normal; word-wrap:normal">1</span><span style="line-height:21px; word-break:normal; word-wrap:normal">).delete()</span></wbr></wbr>