千呼万唤始出来~~~当当当,终于系统要写django的ORM操作啦!!!这里记录的是django操作数据库表一对多、多对多的表创建及操作。对于操作,我们只记录连表相关的内容,介绍增加数据和查找数据,因为能查到就可以用常规方法进行修改,怎么加进来就怎么删掉,都是大同小异,就不再赘述了~~~
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='Eva_J',age=18,user_type_id=1)
2.直接添加外键的对象
obj = models.UserType(caption='test') obj.save() models.UserInfo.objects.create(username='Eva_J',age=18,user_type=obj)
查:
正向查询:根据userinfo查usertype
result = models.UserInfo.objects.filter(user_type__caption='CEO')
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='eva') #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='eva') 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='alex')
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。
查:
#正向查 admin_obj = models.HostAdmin.objects.get(username='alex') print admin_obj.host.all() #反向查 host_obj = models.Host.objects.get(id=3) print host_obj.hostadmin_set.all()
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
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)
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
#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
其他(selecte_related && query):
select_related是用来为连表查询做优化的,我们在查询外键关联的表的时候,都应该使用select_related,这样,只需要执行一条命令就可以把相关的字段都查到了。下面就来看看select_related的作用吧~
例:
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
1 class UserType(models.Model): 2 caption = models.CharField(max_length=32) 3 def __unicode__(self): 4 return self.caption 5 6 7 class UserInfo(models.Model): 8 user_type = models.ForeignKey(UserType)# user_type对象中封装id,caption 9 username = models.CharField(max_length=32) 10 age = models.IntegerField() 11 def __unicode__(self): 12 return self.username
python代码:
result = models.UserInfo.objects.all() result_sr = models.UserType.objects.select_related().all() print result.query print result_sr.query
生成的sql:
SELECT "app01_userinfo"."id", "app01_userinfo"."user_type_id", "app01_userinfo"."username", "app01_userinfo"."age" FROM "app01_userinfo"
SELECT "app01_usertype"."id", "app01_usertype"."caption" FROM "app01_usertype"
这里顺便再介绍一下query方法,可以获取到django为我们生成的sql内容~就是这么炫酷!
其他(F和Q):
未完待续......