Django ORM 練習題

代碼目錄結構

|-- djago_study
|-- manage.py
|-- test_django.py
|-- app01
| |-- admin.py
| |-- apps.py
| |-- models.py
| |-- tests.py
| |-- views.py
| |-- init.py
| |-- migrations
| |-- 0001_initial.py
| |-- init.py
|-- djago_study
| |-- settings.py
| |-- urls.py
| |-- wsgi.py
| |-- init.py
|-- templates

數據表

表 app01_author

id	name	age	phone	detail_id
1	格非	20	1890000000	1
2	邁克爾·湯普森	22	1310000000	2

表 app01_author2book

id	author_id	book_id
1	1	1
2	2	2

表 app01_authordetail

id	hobby	addr
1	踢毽子	北京
2	看書	上海
3	逛街	廣州

表 app01_book

id	title	publish_date	price	publisher_id
1	沙河異聞錄	2019-09-29	100.00	1
2	養育男孩	2019-09-03	80.00	2
3	沙河三部曲	2018-10-24	70.00	2

表 app01_publisher

id	name	city
1	北京十月文藝出版社	北京
2	中信出版社	北京

表 django_migrations

id	app	name	applied
1	app01	0001_initial	2019-09-29 07:49:04.899704

./test_django.py

import os


def main():
    os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'djago_study.settings')
    import django
    django.setup()

    from app01 import models
    ret = models.Book.objects.filter(title__contains="沙河")
    print("查找包含沙河的書", ret)
    ret = models.Book.objects.filter(publish_date__year=2018)
    print("查找出版日期2018的書", ret)
    ret = models.Book.objects.filter(price__gt=10)
    print("查找價格大於10的書", ret)
    ret = models.Publisher.objects.filter(city__contains="北京")
    print("查找在北京的出版社", ret)

    ret = models.Book.objects.all().values_list("publisher__name")
    print("查所有書關聯的出版社", ret, "去重後的結果集", ret.distinct())  # distinct 去重

    ret = models.Book.objects.all().order_by("price").reverse()
    print("講所有書，按照價格排序 方法一", ret)
    ret = models.Book.objects.all().order_by("-price").reverse()
    print("講所有書，按照價格排序 方法二", ret)  # - 負號表示倒序

    ret = models.Book.objects.filter(title="沙河異聞錄").values("publisher__city")
    print("查找書籍沙河異聞錄出版社的所在的城市", ret)

    ret = models.Book.objects.filter(title="沙河異聞錄").values("author__detail__hobby")
    print("查找書籍是沙河異聞錄作者的愛好", ret)


if __name__ == '__main__':
    main()

./app01/models.py

# Create your models here.
from django.db import models


# 出版社
class Publisher(models.Model):
    name = models.CharField(max_length=32)
    city = models.CharField(max_length=32)

    def __str__(self):
        return self.name


# 書
class Book(models.Model):
    title = models.CharField(max_length=32)
    publish_date = models.DateField(auto_now_add=True)
    price = models.DecimalField(max_digits=5, decimal_places=2)
    # 創建外鍵，關聯publish
    publisher = models.ForeignKey(to="Publisher", on_delete=models.CASCADE)

    def __str__(self):
        return "書名 {} 價格 {}".format(self.title, self.price)


# 作者
class Author(models.Model):
    name = models.CharField(max_length=32)
    age = models.IntegerField()
    phone = models.IntegerField()
    # 通過through指定第三張表
    # through_fields指定表字段
    books = models.ManyToManyField(to="Book", through="Author2Book", through_fields=("author", "book"))

    detail = models.OneToOneField(to="AuthorDetail", on_delete=models.CASCADE)

    def __str__(self):
        return self.name


# 自己動手 創建作者和書關聯的第三張表
# 此時 在ORM層面
class Author2Book(models.Model):
    id = models.AutoField(primary_key=True)
    # 作者id
    author = models.ForeignKey(to="Author", on_delete=models.CASCADE)
    # 書id
    book = models.ForeignKey(to="Book", on_delete=models.CASCADE)

    class Meta:
        # 建立唯一約束, 保證不可重複
        unique_together = ("author", "book")


# 作者詳情
class AuthorDetail(models.Model):
    # 愛好
    hobby = models.CharField(max_length=32)
    # 地址
    addr = models.CharField(max_length=128)

整套源碼下載地址
https://www.lanzous.com/i6hew4d

相關資料

F查詢操作
https://docs.djangoproject.com/en/2.2/ref/models/expressions/#django.db.models.F
雙下劃線方法操作
https://www.dev2qa.com/what-does-double-underscore-__-means-in-django-model-queryset-objects-filter-method/
Q查詢操作
https://docs.djangoproject.com/en/2.2/ref/models/querysets/#q-objects
聚合查詢示例
https://docs.djangoproject.com/en/2.2/topics/db/aggregation/
查詢教程
https://docs.djangoproject.com/en/2.2/topics/db/queries/
Model字段 AutoField BigIntegerField
https://docs.djangoproject.com/zh-hans/2.2/ref/models/fields/#decimalfield
ORM那些相關操作
https://www.cnblogs.com/liwenzhou/p/8660826.html