Python - Django - ORM F查询和Q查询

from django.db import models


# 出版社
class Publisher(models.Model):
    id = models.AutoField(primary_key=True)
    name = models.CharField(max_length=64, null=False, unique=True)

    def __str__(self):
        return "<Publisher object: {}>".format(self.name)


# 书籍
class Book(models.Model):
    id = models.AutoField(primary_key=True)
    title = models.CharField(max_length=64, null=False, unique=True)
    price = models.DecimalField(max_digits=5, decimal_places=2, default=00.00)  # 最长位数为 5，小数位数为 2，默认值为 00.00
    publisher = models.ForeignKey(to="Publisher", null=True)  # 把 null 设置为 True
    sell_num = models.IntegerField(default=0)  # 书籍的卖出数量
    inventory_num = models.IntegerField(default=1000)  # 书籍的库存数量

    def __str__(self):
        return "<Book object: {}>".format(self.title)


# 作者
class Author(models.Model):
    id = models.AutoField(primary_key=True)
    name = models.CharField(max_length=16, null=False, unique=True)
    book = models.ManyToManyField(to="Book")  # 多对多关联 Book 表，ORM 会自动生成第 3 张表

    def __str__(self):
        return "<Author object: {}>".format(self.name)
from django.db import models