基于表关系的增删改查

Posted 2021-02-12 wrqysrt

创建四表，author，book，publish，author-detail　　存在多对多，一对一，多对一的关系

在models里创建

class Pulish(models.Model):

   id=models.AutoField(primary_key=True)

   name=models.CharField(max_length=32)

  address=models.CharField(max_length=32)

class Book(models.Model):

   id=models.AutoField(primary_key=True)

 name=models.CharField(max_length=32)
 price=models.DecimalField(max_digits=5,decimal_places=2)
 publish_date=models.DateField()

     pulish=models.Foreignkey(to=Pulish,to_field=id)

     author=models.ManyToManyField(to=Author,to_field=id)

 

class Author(models.Model):
    id = models.AutoField(primary_key=True)
    name = models.CharField(max_length=32)
    author_detail = models.OneToOneField(to=‘AuthorDetail‘, to_field=‘id‘)

class AuthorDetail(models.Model):
    id = models.AutoField(primary_key=True)
    age = models.IntegerField()
    telephone = models.BigIntegerField()
    info = models.TextField()


在test测试

import os
import django
os.environ.setdefault("DJANGO_SETTINGS_MODULE", "dj01.settings")
django.setup()

单对单的增删改查
增加
detail=Author_detail.objects.create()

Author.objects.create(author_detail=detail)或者（author_detail_id=detail_id）

删除

删除被依附表字段，依附表会删除

 Author.objects.last().delete()
# Author.objects.filter()[2].delete()

一对一不考虑更新

查询

# 连表查询规则
# 1. 正向逆向概念：从存放外键的表到关系表称之为正向跨表查询，反之称之为逆向查询
# 2. 正向查询通过外键属性名进行跨表查询
# 3. 逆向查询通过关联表对应类名小写进行跨表查询

# 在连表查询规则规则之上，逆向查询遇到多条结果，在类名后再添加_set

# author=Author.objects.first()
# print(author.author_detail.age)
#
# print(AuthorDetail.objects.first().author.name)


多对一

# publish=Publish.objects.create(name=‘oldboy‘,address=‘上海‘)
# publish=Publish.objects.create(name=‘商务出版社‘,address=‘北京‘)
# book=Book.objects.create(name=‘老人与海‘,price=666.66,publish_date=‘2018-8-8‘,publish_id=1)
# book=Book.objects.create(name=‘谁的青春不迷茫‘,price=66.66,publish_date=‘2016-6-6‘,publish_id=3)
# book=Book.objects.create(name=‘洛丽塔‘,price=166.66,publish_date=‘2006-3-3‘,publish_id=3)


# Book.objects.filter(id=1).delete()
# Publish.objects.filter(id=2).delete()
# 删除被依附表字段，依附表会删除

# book=Book.objects.filter(id=2)[0]
# book.publish_id=2
# book.save()


查询

# print(Book.objects.first().publish.address)

# print(Publish.objects.first().book_set.first().price)     里面列表不能用索引


多对多

# book=Book.objects.filter()[0]
# b2=Book.objects.filter()[2]
# a1=Author.objects.filter()[0]
# a2=Author.objects.last()
# book.author.add(a1)
# book.author.add(a2.id)
# b2.author.add(3,10)
# 清空
# book.author.clear()

# 通过id或对象清除author属性某个
# book.author.remove(a2)

# 清除该本书的之前所有关系记录，添加新的关系
# book.author.clear()
# book.author.add(a2.id)

# 去除列表中不存在的值，添加新值
# book.author.set([a1,a2])


查询

# 多对多
# print(Book.objects.last().author.first().name)
# print(Author.objects.last().book_set.last().name)






查询

 __可以将关联的表关联表的属性全部调出来

查询出版社在上海的出版过的所有书的 作者姓名、作者电话、具体出版社名 的相关信息

print(Publish.objects.filter(address__5exact=‘上海‘).values(‘book__author__name‘,‘book__author__author_detail__telephone‘,‘name‘))