STATIC_URL = '/static/'
STATIC_ROOT = os.path.join(BASE_DIR, 'static')
STATICFILES_DIRS = (
 os.path.join(BASE_DIR, 'static'),
 #os.path.join(os.path.dirname(__file__), '../static/').replace('\\', '/'),
)

class UserType(models.Model):
 caption = models.CharField(max_length=32)
 
class UserInfo(models.Model):
 user = models.CharField(max_length=32)
 email = models.EmailField()
 user_type = models.ForeignKey(to="UserType",to_field="id",on_delete=models.CASCADE)

class UserType(models.Model):
 caption = models.CharField(max_length=32)
 
class UserInfo(models.Model):
 user = models.CharField(verbose_name='用戶', max_length=32)
 email = models.EmailField()
 user_type = models.ForeignKey(to="UserType",to_field="id",on_delete=models.CASCADE)
-----------上面是的是在models.py,下面的是在views.py-------------
def test(requset):
 ut = models.UserType.objects.filter(id=1).first()
 #print(ut)
 models.UserInfo.objects.create(user='小明',email='abc@163.com',user_type=ut)
 return HttpResponse('ok')

class ForeignKey(ForeignObject):
 def __init__(self, to, on_delete, related_name=None, related_query_name=None,
 limit_choices_to=None, parent_link=False, to_field=None,
 db_constraint=True, **kwargs):
  super().__init__(to, on_delete, from_fields=['self'], to_fields=[to_field], **kwargs)

OneToOneField(ForeignKey)
  to,   # 要進(jìn)行關(guān)聯(lián)的表名
  to_field=None    # 要關(guān)聯(lián)的表中的字段名稱
  on_delete=None,    # 當(dāng)刪除關(guān)聯(lián)表中的數(shù)據(jù)時(shí)，當(dāng)前表與其關(guān)聯(lián)的行的行為
 
 ###### 對(duì)于一對(duì)一 ######
 # 1. 一對(duì)一其實(shí)就是 一對(duì)多 + 唯一索引
 # 2.當(dāng)兩個(gè)類(lèi)之間有繼承關(guān)系時(shí)，默認(rèn)會(huì)創(chuàng)建一個(gè)一對(duì)一字段
 # 如下會(huì)在A表中額外增加一個(gè)c_ptr_id列且唯一：
class C(models.Model):
nid = models.AutoField(primary_key=True)
part = models.CharField(max_length=12)
 
class A(C):
id = models.AutoField(primary_key=True)
code = models.CharField(max_length=1)

class OneToOneField(ForeignKey):
 def __init__(self, to, on_delete, to_field=None, **kwargs):
  kwargs['unique'] = True
  super().__init__(to, on_delete, to_field=to_field, **kwargs)

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)這里可以直接對(duì)第三張表直接操

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") --------------> appname_application_r 表名

obj = models.Application.objects.get(id=1)
obj.name
 
# 第三張表操作：HostToApp table   基于id=1的Application添加對(duì)應(yīng)關(guān)系
obj.r.add(1)增
obj.r.add(2)
obj.r.add(2,3,4)
obj.r.add(*[1,2,3,4])
 
obj.r.remove(1)   刪
obj.r.remove(2,4)
obj.r.remove(*[1,2,3])
 
obj.r.clear() 清除app_id =1 的列
 
obj.r.set([3,5,7])   改set將原來(lái)數(shù)據(jù)庫(kù)中的關(guān)系先全部刪除，在添加1-3，1-5，1-7
——————————————————————————
# 所有相關(guān)的主機(jī)對(duì)象“列表” QuerySet
obj.r.all()   obj.filter() obj.first()

  ｛%for app in app_list%｝
  <tr>
 <td>{{app.name}}</td>
 <td>{{app.r.all}}</td>
   </tr>
  ｛%endfor%｝

class ManyToManyField(RelatedField):
 def __init__(self, to, related_name=None, related_query_name=None,
 limit_choices_to=None, symmetrical=None, through=None,
 through_fields=None, db_constraint=True, db_table=None,
 swappable=True, **kwargs):
  super().__init__(**kwargs)