建立模型

from django.db import models

class Reporter(models.Model):
    first_name = models.CharField(max_length=30)
    last_name = models.CharField(max_length=30)
    email = models.EmailField()

    def __str__(self):
        return "%s %s" % (self.first_name, self.last_name)

 
class Article(models.Model):
    headline = models.CharField(max_length=100)
    pub_date = models.DateField()
    reporter = models.ForeignKey(Reporter, on_delete=models.CASCADE)

    def __str__(self):
        return self.headline

    class Meta:
        ordering = ('headline',)

資料遷移

#生成遷移檔案，記錄下在models.py檔案中的改動
python manage.py makemigrations 

##將改動的內容作用於資料庫，生成相應的資料
python manage.py migrate

表操作

建立資料

>>> #建立幾個記者
>>> r = Reporter(first_name='John', last_name='Smith', email='[email protected]')
>>> r.save()

 
>>> r2 = Reporter(first_name='Paul', last_name='Jones', email='[email protected]')
>>> r2.save()


>>> #建立一篇文章
>>> from datetime import date
>>> a = Article(id=None, headline="This is a test", pub_date=date(2005, 7, 27), reporter=r)
>>> a.save()

>>> a.reporter.id
1

>>> a.reporter
<Reporter: John Smith>


>>> #通過Reporter物件建立文章
>>> new_article = r.article_set.create(headline="John's second story", pub_date=date(2005, 7, 29))
>>> new_article
<Article: John's second story>
>>> new_article.reporter
<Reporter: John Smith>
>>> new_article.reporter.id
1

查詢方法

>>>#反向查詢，過濾出 Article 中以 'This' 開頭的 headline
>>>r.article_set.filter(headline__startswith='This')
<QuerySet [<Article: This is a test>]>


>>># 查詢 Articles 中關聯物件  Reporter 的 first name 是 "John" 的所有文章,這裡是完全匹配 （first name = "John"）
>>> Article.objects.filter(reporter__first_name='John')
<QuerySet [<Article: John's second story>, <Article: This is a test>]>


>>>#查詢兩次相關欄位, 這將轉換為WHERE子句中的AND條件
>>> Article.objects.filter(reporter__first_name='John', reporter__last_name='Smith')
<QuerySet [<Article: John's second story>, <Article: This is a test>]>

>>>#對於關聯查詢，可以提供主鍵值或顯式傳遞關聯物件
>>> Article.objects.filter(reporter__pk=1)
<QuerySet [<Article: John's second story>, <Article: This is a test>]>
>>> Article.objects.filter(reporter=1)
<QuerySet [<Article: John's second story>, <Article: This is a test>]>
>>> Article.objects.filter(reporter=r)
<QuerySet [<Article: John's second story>, <Article: This is a test>]>

>>> # __in
>>> Article.objects.filter(reporter__in=[1,2]).distinct()
<QuerySet [<Article: John's second story>, <Article: Paul's story>, <Article: This is a test>]>
>>> Article.objects.filter(reporter__in=[r,r2]).distinct()
<QuerySet [<Article: John's second story>, <Article: Paul's story>, <Article: This is a test>]>

>>>#還可以使用查詢集作為查詢條件
>>>Article.objects.filter(reporter__in=Reporter.objects.filter(first_name='John')).distinct()
<QuerySet [<Article: John's second story>, <Article: This is a test>]>


>>>#反向查詢，以關聯物件 Article 作為條件獲取滿足條件的 Reporter
>>> Reporter.objects.filter(article__pk=1)
<QuerySet [<Reporter: John Smith>]>
>>> Reporter.objects.filter(article=1)
<QuerySet [<Reporter: John Smith>]>
>>> Reporter.objects.filter(article=a)
<QuerySet [<Reporter: John Smith>]>

>>> Reporter.objects.filter(article__headline__startswith='This')
<QuerySet [<Reporter: John Smith>, <Reporter: John Smith>, <Reporter: John Smith>]>
>>> Reporter.objects.filter(article__headline__startswith='This').distinct()
<QuerySet [<Reporter: John Smith>]>


>>> #計數 count()
>>>Reporter.objects.filter(article__headline__startswith='This').count()
3

>>> #去重後計數
>>>Reporter.objects.filter(article__headline__startswith='This').distinct().count()
1

 轉移資料---add(obj)

>>>#建立一篇新文章
>>> new_article2 = Article.objects.create(headline="Paul's story", pub_date=date(2006, 1, 17), reporter=r)
>>> new_article2.reporter
<Reporter: John Smith>
>>> new_article2.reporter.id
1
>>> r.article_set.all()
<QuerySet [<Article: John's second story>, <Article: Paul's story>, <Article: This is a test>]>

>>> #將new_article2文章轉移到 r2 ，r 與這篇文章就沒有關聯了
>>> r2.article_set.add(new_article2)
>>> new_article2.reporter.id
2
>>> new_article2.reporter
<Reporter: Paul Jones>

>>> r.article_set.all()
<QuerySet [<Article: John's second story>, <Article: This is a test>]>
>>> r2.article_set.all()
<QuerySet [<Article: Paul's story>]>

>>> r.article_set.count()
2

>>> r2.article_set.count()
1

刪除資料---delete()

>>>#可以先獲取 Reporter 後再刪除
>>> Article.objects.all()
<QuerySet [<Article: John's second story>, <Article: Paul's story>, <Article: This is a test>]>
>>> Reporter.objects.order_by('first_name')
<QuerySet [<Reporter: John Smith>, <Reporter: Paul Jones>]>
>>> r2.delete()
>>> Article.objects.all()
<QuerySet [<Article: John's second story>, <Article: This is a test>]>
>>> Reporter.objects.order_by('first_name')
<QuerySet [<Reporter: John Smith>]>


>>>#可以在查詢中使用聯接 delete() 直接刪除：
>>>Reporter.objects.filter(article__headline__startswith='This').delete()
>>> Reporter.objects.all()
<QuerySet []>
>>> Article.objects.all()
<QuerySet []>

學習自用，歡迎大神評論、指正
詳情見Django文件：

https://docs.djangoproject.com/en/2.1/topics/db/examples/many_to_one/