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  • django ORM多对多操作

    创建多对多:
    	方式一:自定义关系表
    		class Host(models.Model):
    			nid = models.AutoField(primary_key=True)
    			hostname = models.CharField(max_length=32,db_index=True)
    			ip = models.GenericIPAddressField(protocol="ipv4",db_index=True)
    			port = models.IntegerField()
    			b = models.ForeignKey(to="Business", to_field='id')
    		# 10
    		class Application(models.Model):
    			name = models.CharField(max_length=32)
    		# 2
    		
    		class HostToApp(models.Model):
    			hobj = models.ForeignKey(to='Host',to_field='nid')
    			aobj = models.ForeignKey(to='Application',to_field='id')
    			
    		# HostToApp.objects.create(hobj_id=1,aobj_id=2)
    						
    	方式二:自动创建关系表
    		class Host(models.Model):
    			nid = models.AutoField(primary_key=True)
    			hostname = models.CharField(max_length=32,db_index=True)
    			ip = models.GenericIPAddressField(protocol="ipv4",db_index=True)
    			port = models.IntegerField()
    			b = models.ForeignKey(to="Business", to_field='id')
    		# 10
    		class Application(models.Model):
    			name = models.CharField(max_length=32)
    			r = models.ManyToManyField("Host")
    			
    		无法直接对第三张表进行操作
    		
    		obj = Application.objects.get(id=1)
    		obj.name
    		
    		# 第三张表操作
    		obj.r.add(1)
    		obj.r.add(2)
    		obj.r.add(2,3,4)
    		obj.r.add(*[1,2,3,4])
    		
    		obj.r.remove(1)
    		obj.r.remove(2,4)
    		obj.r.remove(*[1,2,3])
    		
    		obj.r.clear()
    		
    		
    		# 所有相关的主机对象“列表” QuerySet
    		obj.r.all()
    

      

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  • 原文地址:https://www.cnblogs.com/alex-hrg/p/10139045.html
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