关联查询
#coding=utf8
from django.db import models
# Create your models here.
# coding=utf8
from django.db import models
# Create your models here.
class Book(models.Model):
title = models.CharField(max_length=64)
price = models.IntegerField()
color = models.CharField(max_length=64)
page_num = models.IntegerField(null=True)
publisher = models.ForeignKey("Publisher") # 外键，从此处进行关联查询
def __str__(self):
return self.title.encode("utf-8")
class Author(models.Model):
name = models.CharField(max_length=30)
def __str__(self):
return self.name.encode("utf-8")
# 自己写第三张表 多对多 book - author
class Book2Author(models.Model):
author = models.ForeignKey("Author")
book = models.ForeignKey("Book")
# state = models.CharField(max_length=64)
class Meta:
unique_together = ["author","book"] # 联合唯一
class Publisher(models.Model):
name = models.CharField(max_length=64)
city = models.CharField(max_length=63) #
def __str__(self):
return self.city.encode("utf-8")
正向查找：从对象按照它的属性查找
从书本《go》的publisher字段查到出版社，再通过此出版社查到出版社的地址
ob = models.Book.objects.filter(title="go")[0]
print(ob.publisher.city)
ob即是《go》书的出版社对象
反向查找：
ob = models.Publisher.objects.filter(id=2)[0]
print(ob.book_set.all().values("title"))
反向使用book_set查询，通过values查book的字段，如果需要，还可以使用distinct()去重。
