django model 查詢 筆記二 ：多對多查詢

# -*- coding:utf-8 -*-
   # 沒法貼鏈接，參考自 CSDN：shangliuyan,好像沒法貼鏈接，打出名字特此感謝，如有問題請留
from django.db import models


# 主表
class Author(models.Model):
    first_name = models.CharField(max_length=30)
    last_name = models.CharField(max_length=40)
    email = models.EmailField()


# 從表
class Book(models.Model):
    title = models.CharField(max_length=200)
    authors = models.ManyToManyField(Author)

# 從表查主表
b = Book.objects.get(id=50)
b.authors.all()
b.authors.filter(first_name='Adam')

# 主表查從表
a = Author.objects.get(id=1)
a.book_set.all()

# 添加對象
a = Author.objects.get(id=1)
b = Book.objects.get(id=50)
b.authors.add(a)

# 刪除對象
a = Author.objects.get(id=1)  
b = Book.objects.get(id=50)  
b.authors.remove(a) 或者 b.authors.filter(id=1).delete()