Python之Django--ORM连表操作

一对多

class UserType(models.Model):
    caption = models.CharField(max_length=32)

class UserInfo(models.Model):
    user_type = models.ForeignKey(UserType)# user_type对象中封装id,caption
    username = models.CharField(max_length=32)
    age = models.IntegerField()

增：

1.外键id添加 

models.UserInfo.objects.create(username='xs',age=19,user_type_id=1)

2.直接添加外键的对象

obj = models.UserType(caption='haha')
obj.save()
models.UserInfo.objects.create(username='xs',age=18,user_type=obj)

查：

　　正向查询：根据userinfo查usertype

result = models.UserInfo.objects.filter(user_type__caption='CTO')
for item in result:
    print item.username,item.age,item.user_type.caption

　　反向查询：根据usertype查userinfo

result = models.UserType.objects.get(id=1)
    print '-->0',result
    print '-->1',result.userinfo_set
    print '-->2',result.userinfo_set.all()
    print '-->3',result.userinfo_set.filter(username='xs') #用字段条件查询
    print '-->4',models.UserInfo.objects.filter(user_type=result) #用对象条件查询

    user_type_obj = models.UserType.objects.get(userinfo__username='xs')
    print '-->0',user_type_obj.caption
    print '-->1',user_type_obj.userinfo_set.all().count()
    return HttpResponse('ok')

多对多

class Host(models.Model):
    hostname = models.CharField(max_length=32)
    port = models.IntegerField()

class HostAdmin(models.Model):
    username = models.CharField(max_length=32)
    email = models.CharField(max_length=32)
    host = models.ManyToManyField(Host)

增：

　　正向增：

admin_obj = models.HostAdmin.objects.get(username='xs')
host_list = models.Host.objects.filter(id__lt=3)
admin_obj.host.add(*host_list)

　　反向增：

host_obj = models.Host.objects.get(id=3)
admin_list= models.HostAdmin.objects.filter(id__gt=1)
host_obj.hostadmin_set.add(*admin_list)

区别总结：区别在于正向查拥有自己创建好的host句柄，可以直接使用add方法添加，而反向查没有，所以要使用django为我们提供的set句柄。

#正向增加

admin_obj = models.HostAdmin.objects.get(username='xs')
host_list = models.Host.objects.filter(id__lt=3)
admin_obj.host.add(*host_list)

#反向添加

host_obj = model.Host.objects.get(id=3)
admin_list = models.HostAdmin.objects.filter(id__gt=1)
host_obj.hostadmin_set.add(*admin_list)

查:

#正向查
    admin_obj = models.HostAdmin.objects.get(username='xs')
    print admin_obj.host.all()
 #反向查
    host_obj = models.Host.objects.get(id=3)
    print host_obj.hostadmin_set.all()

class Host1(models.Model):
    hostname = models.CharField(max_length=32)
    port = models.IntegerField()

class HostAdmin1(models.Model):
    username = models.CharField(max_length=32)
    email = models.CharField(max_length=32)
    host = models.ManyToManyField(Host1,through='HostRelation')

class HostRelation(models.Model):
    host =models.ForeignKey(Host1)
    admin =models.ForeignKey(HostAdmin1)

#增
    #models.HostRelation.objects.create(host_id=1,admin_id=1)
    #查
    relationList = models.HostRelation.objects.all()
    for item in relationList:
        print item.host.hostname
        print item.admin.username