Orm - 一对一、一对多、多对多

models.py

from django.db import models
# Create your models here.
class author(models.Model):
    name = models.CharField(max_length=255)
    age = models.IntegerField()
    # 一对一 默认会和id做集联
    # authorDetail表没有数据后会报错
    authorDetail = models.OneToOneField(to="authorDetail",on_delete=models.CASCADE)  # 与authorDetail表做集联
    # authorDetail表没有数据后 authorDetail = null
    # authorDetail = models.OneToOneField(to="authorDetail",on_delete=models.SET_NULL)  # 不与authorDetail表做集联
class authorDetail(models.Model):
    birthday = models.DateField()
    telephone = models.CharField(max_length=255)
    addr = models.CharField(max_length=255)
# 出版社
class Publish(models.Model):
    name = models.CharField(max_length=255)
    city = models.CharField(max_length=255)
    email = models.EmailField()
# 书籍表
class Books(models.Model):
    bid = models.AutoField(primary_key=True)
    title = models.CharField(max_length=255)
    publisdate = models.DateField()
    price = models.DecimalField(max_digits=5,decimal_places=2)
    publishs = models.ForeignKey(to="Publish",to_field="id",on_delete=models.CASCADE)
    authors = models.ManyToManyField(to="author")   # 自动创建第三张表，关联另外两张表的主键字段
# class bookstoauthor(models.Model):
#     book_id = models.ForeignKey(to="Books")
#     author_id = models.ForeignKey(to="author")

app/init.py

import pymysql
pymysql.install_as_MySQLdb()

数据库生成表

python manage.py makemigrations
python manage.py migrate

会生成5张表

其中 test01_books_authors 表记录了 多对多表的id关联关系