创建模型

from django.db import modelsclass Publication(models.Model):    title = models.CharField(max_length=30)    def __str__(self):        return self.title    class Meta:        ordering = ('title',)class Article(models.Model):    headline = models.CharField(max_length=100)    publications = models.ManyToManyField(Publication)    def __str__(self):        return self.headline    class Meta:        ordering = ('headline',)

 

数据迁移

#生成迁移文件，记录下在models.py文件中的改动python manage.py makemigrations ##将改动的内容作用于数据库，生成相应的数据python manage.py migrate

 

表操作

创建数据

执行 python manage.py shell，创建Publication和Article数据

>>> p1 = Publication(title='The Python Journal')>>> p1.save()>>> p2 = Publication(title='Science News')>>> p2.save()>>> p3 = Publication(title='Science Weekly')>>> p3.save()>>> a1 = Article(headline='Django lets you build Web apps easily')>>> a1.save()>>> a1.publications.add(p1)>>> a2 = Article(headline='NASA uses Python')>>> a2.save()>>> a2.publications.add(p1, p2)#可以同时添加多个publication对象>>> a2.publications.add(p3)>>> a2.publications.add(a1)#添加错误类型会引发TypeErrorTraceback (most recent call last):...TypeError: 'Publication' instance expected>>> #可以用 Article 对象调用 create() 创建 并 添加 publications>>> new_publication = a2.publications.create(title='Highlights for Children')>>> # Article 对象 可以访问相关联的 publications 对象>>> a1.publications.all()
      
       ]>>>> a2.publications.all()
       
        , 
        
         , 
         
          , 
          
           ]>>>> #publications 对象 可以访问相关联的 Article 对象>>> p2.article_set.all()
           
            ]>>>> p1.article_set.all()
            
             , 
             
              ]>>>> Publication.objects.get(id=4).article_set.all()
              
               ]>
              
             
            
           
          
         
        
       
      

 

查询方法

>>> #跨表查询>>> Article.objects.filter(publications__id=1)
      
       , 
       
        ]>>>> Article.objects.filter(publications__pk=1)
        
         , 
         
          ]>>>> Article.objects.filter(publications=1)
          
           , 
           
            ]>>>> Article.objects.filter(publications=p1)
            
             , 
             
              ]>>>>Article.objects.filter(publications__title__startswith="Science")
              
               , 
               
                ]>>>>Article.objects.filter(publications__title__startswith="Science").distinct() #去重
                
                 ]>>>> Article.objects.filter(publications__in=[1,2]).distinct()
                 
                  , 
                  
                   ]>>>> Article.objects.filter(publications__in=[p1,p2]).distinct()
                   
                    , 
                    
                     ]>>>> #反向查询>>> Publication.objects.filter(id=1)
                     
                      ]>>>> Publication.objects.filter(pk=1)
                      
                       ]>>>>Publication.objects.filter(article__headline__startswith="NASA")
                       
                        , 
                        
                         , 
                         
                          , 
                          
                           ]>>>> Publication.objects.filter(article__id=1)
                           
                            ]>>>> Publication.objects.filter(article__pk=1)
                            
                             ]>>>> Publication.objects.filter(article=1)
                             
                              ]>>>> Publication.objects.filter(article=a1)
                              
                               ]>>>> Publication.objects.filter(article__in=[1,2]).distinct()
                               
                                , 
                                
                                 , 
                                 
                                  , 
                                  
                                   ]>>>> Publication.objects.filter(article__in=[a1,a2]).distinct()
                                   
                                    , 
                                    
                                     , 
                                     
                                      , 
                                      
                                       ]>>>> #排除 exclude 一样有效>>> Article.objects.exclude(publications=p2)
                                       
                                        ]>
                                       
                                      
                                     
                                    
                                   
                                  
                                 
                                
                               
                              
                             
                            
                           
                          
                         
                        
                       
                      
                     
                    
                   
                  
                 
                
               
              
             
            
           
          
         
        
       
      

 

删除数据---delete()

delete() 会删除对象的引用，其他关联对象的引用都会被删除

>>> #删除Publication，Article将无法访问>>> p1.delete()>>> Publication.objects.all()
      
       , 
       
        , 
        
         ]>>>> a1 = Article.objects.get(pk=1)>>> a1.publications.all()#此a1关联对象被删除，已经不存在了，调用get(id=1) 会报错
         
          >>> #删除Article， Publication将无法访问>>> a2.delete()>>> Article.objects.all()
          
           ]>>>> p2.article_set.all()
           
          
         
        
       
      

 

添加数据---add()

>>> #通过M2M的“另一端”添加关联对象>>> a4 = Article(headline='NASA finds intelligent life on Earth')>>> a4.save()>>> p2.article_set.add(a4) #Publication添加关联对象>>> p2.article_set.all()
      
       ]>>>> a4.publications.all()
       
        ]>>>> #通过另一端创建并添加关键字>>> new_article = p2.article_set.create(headline='Oxygen-free diet works wonders')>>> p2.article_set.all()
        
         , 
         
          ]>>>> a5 = p2.article_set.all()[1]>>> a5.publications.all()
          
           ]>
          
         
        
       
      

 

移除数据---remove()

remove() 只移除当前对象的关联实例

>>> #从Article移除Publication>>> a4.publications.remove(p2)#只移除a4这个实例中的p2,其他实例中的并没有移除p2>>> p2.article_set.all()
      
       ]>>>> a4.publications.all()
       
        >>> # 从Publication移除Article>>> p2.article_set.remove(a5)>>> p2.article_set.all()
        
         >>> a5.publications.all()
         
        
       
      

 

设置、清除关系集合---set([..., ...])、clear()

>>> #设置关系集>>> a4.publications.all()
      
       ]>>>> a4.publications.set([p3])#可以在list中添加多个，相当于把a4关联的所有publications全都替换掉>>> a4.publications.all()
       
        ]>>>> #清除关系集>>> p2.article_set.clear()>>> p2.article_set.all()
        
         >>> #从另一端清除>>> p2.article_set.add(a4, a5)>>> p2.article_set.all()
         
          , 
          
           ]>>>> a4.publications.all()
           
            , 
            
             ]>>>> a4.publications.clear()>>> a4.publications.all()
             
              >>> p2.article_set.all()
              
               ]>
              
             
            
           
          
         
        
       
      

 

学习自用，欢迎大神评论、指正

详情见Django文档：