Django ORM多对多查询方法(自定义第三张表&ManyToManyField)

 # models.py class Boy(models.Model): name = models.CharField(max_length=32) class Girl(models.Model): name = models.CharField(max_length=32) class Love(models.Model): b = models.ForeignKey('Boy') g = models.ForeignKey('Girl') # 创建联合唯一索引 # class Meta: #   unique_together = [ #     ('b','g')， #   ] # views.py def test(request): # objs = [ #   models.Boy(name='summer'), #   models.Boy(name='spring'), #   models.Boy(name='autumn'), # ] # models.Boy.objects.bulk_create(objs,5) # objs = [ #   models.Girl(name='小于'), #   models.Girl(name='小秋'), #   models.Girl(name='小夏'), # ] # models.Girl.objects.bulk_create(objs,5) # 查询和girl小于有关系的boy # 1 通过girl表进行反向查找 obj = models.Girl.objects.filter(name='小于').first().love_set.all() # obj = models.Girl.objects.filter(name='小于').first().love_set.select_related('b').all() for i in obj: print(i.b.name) print(' '.center(60,'=')) # 2 通过Love表进行查找 obj = models.Love.objects.filter(g__name='小于').all() for i in obj: print(i.b.name) # 这样进行查询性能不好，需要重新发sql请求在进行查询另外一张表中的数据 boy_list = models.Love.objects.filter(g__name='小于').values('b__name') for i in boy_list: print(i['b__name']) # 这样 进行了 优化 不会重复发送sql请求，查询到的结果内是字典 boy_obj = models.Love.objects.filter(g__name='小于').select_related('b').all() for i in boy_obj: print(i.b.name) # select_related('ut') 相当 于 inner join 先连成一张表再进行查询 return HttpResponse('insert ok ....') 

 # models.py from django.db import models class Boy(models.Model): name = models.CharField(max_length=32) # m = models.ManyToManyField('Girl') class Girl(models.Model): name = models.CharField(max_length=32) m = models.ManyToManyField('Boy') # views.py def test(request): # objs = [ #   models.Boy(name='summer'), #   models.Boy(name='spring'), #   models.Boy(name='autumn'), # ] # models.Boy.objects.bulk_create(objs,5) # objs = [ #   models.Girl(name='小于'), #   models.Girl(name='小秋'), #   models.Girl(name='小夏'), # ] # models.Girl.objects.bulk_create(objs,5) # ManyToManyField obj = models.Girl.objects.filter(name='小秋').first() # 增 # obj.m.add(3) # obj.m.add(3,4) # obj.m.add(*[1,2]) # 删 # obj.m.remove(3) # obj.m.remove(3,4) # obj.m.remove(*[1,2]) # 改 # obj.m.set([1,2,]) # boy_obj = obj.m.all() # for row in boy_obj: #   print(row.id,row.name) # 清除 # obj.m.clear() # 反向查 在没有 ManyToManyField 字段的表中查 obj = models.Boy.objects.filter(name='summer').first() girl_obj = obj.girl_set.all() # 增删改查 obj.girl_set.set([1,2,3]) for row in girl_list: print(row.id,row.name) return HttpResponse('ok') 

 # modles.py class Boy(models.Model): name = models.Ch<a style="color:transparent">来源gao($daima.com搞@代@#码(网</a>arField(max_length=32) class Girl(models.Model): name = models.CharField(max_length=32) m = models.ManyToManyField('Boy',through='Love',through_fields=('b','g')) # 只让其生成3张表，如果不加后面产生生成4张表 class Love(models.Model): b = models.ForeignKey('Boy') g = models.ForeignKey('Girl') # views.py def test(request): obj = models.Girl.objects.filter(name='小于').first() # obj.m.add(1) # 不行 # obj.m.remove(1) # 不行 # obj.m.set([1,2]) # 不行 # obj.m.clear() # 可以 # obj.m.all() # 可以 # 杂交的方法对获取查询方便点，还添加了清空功能 boy_obj = obj.m.all() for i in boy_obj: print(i.name)