orm 扩展

"""
ORM小练习

如何在一个Python脚本或文件中加载Django项目的配置和变量信息
"""

import os

if __name__ == '__main__':
# 加载Django项目的配置信息
os.environ.setdefault("DJANGO_SETTINGS_MODULE", "ormday69.settings")
# 导入Django，并启动Django项目
import django
django.setup()

from app01 import models
# # 查询所有的人
# ret = models.Person.objects.all()
# print(ret)
# # get查询
# ret = models.Person.objects.get(name="小黑")
# print(ret)
# # filter
# ret = models.Person.objects.filter(id=100) # 不存在返回一个空的QuerySet，不会报错
# print(ret)
# # 就算查询的结果只有一个，返回的也是QuerySet，我们要用索引的方式取出第一个元素
# ret = models.Person.objects.filter(id=1)[0]
# print(ret)
# print("exclude".center(80, "*"))
# # exclude
# ret = models.Person.objects.exclude(id=1)
# print(ret)
# print("values".center(80, "*"))
# # values 返回一个QuerySet对象，里面都是字典。不写字段名，默认查询所有字段
# ret = models.Person.objects.values("name", "birthday")
# print(ret)
# print("values_list".center(80, "*"))
# # values_list 返回一个QuerySet对象，里面都是元祖。不写字段名，默认查询所有字段
# ret = models.Person.objects.values_list()
# print(ret)
# print("order_by".center(80, "*"))
# # order_by 按照指定的字段排序
# ret = models.Person.objects.all().order_by("birthday")
# print(ret)
# print("reverse".center(80, "*"))
# # reverse 将一个有序的QuerySet 反转顺序
# # 对有序的QuerySet才能调用reverse
# ret = models.Person.objects.all().reverse()
# print(ret)
# print("count".center(80, "*"))
# # count 返回QuerySet中对象的数量
# ret = models.Person.objects.all().count()
# print(ret)
# print("first".center(80, "*"))
# # first 返回QuerySet中第一个对象
# ret = models.Person.objects.all().first()
# print(ret)
# print("last".center(80, "*"))
# # last 返回QuerySet中最后一个对象
# ret = models.Person.objects.all().last()
# print(ret)
# print("exists".center(80, "*"))
# # exists 判断表里有没有数据
# ret = models.Book.objects.exists()
# print(ret)

# 单表查询之神奇的双下划线
# # 查询id值大于1小于4的结果
# ret = models.Person.objects.filter(id__gt=1, id__lt=4)
# print(ret)
# # in
# # 查询 id 在 [1, 3, 5, 7]中的结果
# ret = models.Person.objects.filter(id__in=[1, 3, 5, 7])
# print(ret)
# ret = models.Person.objects.exclude(id__in=[1, 3, 5, 7])
# print(ret)
# # contains 字段包含指定值的
# # icontains 忽略大小写包含指定值
# ret = models.Person.objects.filter(name__contains="小")
# print(ret)
# # range
# # 判断id值在哪个区间的 SQL语句中的between and 1<= <=3
# ret = models.Person.objects.filter(id__range=[1,3])
# print(ret)
# # 日期和时间字段还可以有以下写法
# ret = models.Person.objects.filter(birthday__year=2000)
# print(ret)
# ret = models.Person.objects.filter(birthday__year=2000, birthday__month=5)
# print(ret)

# 外键的查询操作

# 正向查询
# 基于对象跨表查询
# book_obj = models.Book.objects.all().first()
# ret = book_obj.publisher # 和我这本书关联的出版社对象
# print(ret, type(ret))
# ret = book_obj.publisher.name # 和我这本书关联的出版社对象
# print(ret, type(ret))

# 查询id是1的书的出版社的名称
# 利用双下划线跨表查询
# 双下划线就表示跨了一张表
# ret = models.Book.objects.filter(id=1).values_list("publisher__name")
# print(ret)

# 反向查询
# 1. 基于对象查询
# publisher_obj = models.Publisher.objects.get(id=1) # 得到一个具体的对象
# # ret = publisher_obj.book_set.all()
# ret = publisher_obj.books.all()
# print(ret)
#
# # 2. 基于双下划线
# ret = models.Publisher.objects.filter(id=1).values_list("xxoo__title")
# print(ret)

# 多对多
# 查询
# author_obj = models.Author.objects.first()
# print(author_obj.name)
# 查询金老板写过的书
# ret = author_obj.books.all()
# print(author_obj.books, type(author_obj.books))
# print(ret)
# 1. create
# 通过作者创建一本书,会自动保存
# 做了两件事：
# 1. 在book表里面创建一本新书，2. 在作者和书的关系表中添加关联记录
# author_obj.books.create(title="金老板自传", publisher_id=2)
# 2. add
# 在金老板关联的书里面，再加一本id是4的书
# book_obj = models.Book.objects.get(id=4)
# author_obj.books.add(book_obj)
# 添加多个
# book_objs = models.Book.objects.filter(id__gt=5)
# author_obj.books.add(*book_objs) # 要把列表打散再传进去
# 直接添加id
# author_obj.books.add(9)

# remove
# 从金老板关联的书里面把开飞船删掉
# book_obj = models.Book.objects.get(title="跟金老板学开飞船")
# author_obj.books.remove(book_obj)
# 从金老板关联的书里面把 id是8的记录删掉
# author_obj.books.remove(8)

# clear
# 清空
# 把景女神关联的所有书都删掉
# jing_obj = models.Author.objects.get(id=2)
# jing_obj.books.clear()

# 额外补充的，外键的反向操作

# 找到id是1的出版社
# publisher_obj = models.Publisher.objects.get(id=2)
# publisher_obj.books.clear()

# 聚合
from django.db.models import Avg, Sum, Max, Min, Count
# ret = models.Book.objects.all().aggregate(price_avg=Avg("price"))
# print(ret)
#
# ret = models.Book.objects.all().aggregate(price_avg=Avg("price"), price_max=Max("price"), price_min=Min("price"))
# print(ret)
# print(ret.get("price_max"), type(ret.get("price_max")))

# 分组查询

# 查询每一本书的作者个数
# ret = models.Book.objects.all().annotate(author_num=Count("author"))
# # print(ret)
# for book in ret:
# print("书名：{}，作者数量：{}".format(book.title, book.author_num))

# 查询作者数量大于1的书
# ret = models.Book.objects.all().annotate(author_num=Count("author")).filter(author_num__gt=1)
# print(ret)

# 查询各个作者出的书的总价格
# ret = models.Author.objects.all().annotate(price_sum=Sum("books__price")).values_list("name", "price_sum")
# ret = models.Author.objects.all().annotate(price_sum=Sum("books__price"))
# print(ret)
# for i in ret:
# print(i, i.name, i.price_sum)
# print(ret.values_list("id", "name", "price_sum"))

# F和Q
# ret = models.Book.objects.filter(price__gt=9.99)
# print(ret)

# 查询出库存数大于卖出数的所有书（两个字段做比较）
from django.db.models import F
# ret = models.Book.objects.filter(kucun__gt=F("maichu"))
# print(ret)
# 刷单把每一本书的卖出数都乘以3
# obj = models.Book.objects.first()
# obj.maichu = 1000 * 3
# obj.save()
# 具体的对象没有update()，QuerySet对象才有update()方法。

# models.Book.objects.update(maichu=(F("maichu")+1)*3)

# 给每一本书的书名后面加上第一版
# from django.db.models.functions import Concat
# from django.db.models import Value
#
# models.Book.objects.update(title=Concat(F("title"), Value("第一版")))

# Q查询
from django.db.models import Q
# 查询卖出数大于1000，并且价格小于100的所有书
# ret = models.Book.objects.filter(maichu__gt=1000, price__lt=100)
# print(ret)
# 查询卖出数大于1000，或者价格小于100的所有书
# ret = models.Book.objects.filter(Q(maichu__gt=1000) | Q(price__lt=100))
# print(ret)
# Q查询和字段查询同时存在时，字段查询要放在Q查询的后面
# ret = models.Book.objects.filter(Q(maichu__gt=1000) | Q(price__lt=100), title__contains="金老板")
# print(ret)

# Django ORM 事务

# try:
# from django.db import transaction
#
# with transaction.atomic():
# # 先创建一个出版社
# new_publisher = models.Publisher.objects.create(name="火星出版社")
# # 创建一本书
# models.Book.objects.create(
# title="橘子物语",
# price=11.11,
# kucun=10,
# maichu=10,
# publisher_id=1000 # 指定一个不存在的出版社id
# )
# except Exception as e:
# print(str(e))

# 没有指定原子操作
# try:
#
# # 先创建一个出版社
# new_publisher = models.Publisher.objects.create(name="火星出版社")
# # 创建一本书
# models.Book.objects.create(
# title="橘子物语",
# price=11.11,
# kucun=10,
# maichu=10,
# publisher_id=1000 # 指定一个不存在的出版社id
# )
# except Exception as e:
# print(str(e))

# 执行原生SQL
# 更高灵活度的方式执行原生SQL语句
# from django.db import connection
# cursor = connection.cursor() # cursor = connections['default'].cursor()
# cursor.execute("SELECT * from app01_book where id = %s", [1])
# ret = cursor.fetchone()
# print(ret)

# 在QuerSet查询的基础上自己指定其他的SQL语句(了解即可)
ret = models.Book.objects.extra(
# 把出版社计数赋值给newid
select={'newid': 'select count(1) from app01_publisher where id>%s'},
select_params=[1, ],

where=["app01_book.id=%s"],

params=[1, ],
tables=['app01_publisher']
)

print(ret)
for i in ret:
print(i)

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orm 扩展

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