Django：ORM基本操作-CRUD，管理器对象objects，-----＞删除：删除单个数据，删除批量数据

Microsoft Windows [版本 10.0.19042.928]
(c) Microsoft Corporation。保留所有权利。C:\Users\520>cd mysiteC:\Users\520\mysite>dir驱动器 C 中的卷是 Windows-SSD卷的序列号是 42D9-2A68C:\Users\520\mysite 的目录2021/05/20  22:47    <DIR>          .
2021/05/20  22:47    <DIR>          ..
2021/06/09  23:54    <DIR>          .idea
2021/05/20  22:47           135,168 db.sqlite3
2021/05/20  22:32               684 manage.py
2021/06/09  23:34    <DIR>          myapp
2021/05/28  23:57    <DIR>          mysite
2021/05/20  22:32    <DIR>          templates
2021/05/20  22:32    <DIR>          venv2 个文件        135,852 字节7 个目录 425,407,660,032 可用字节C:\Users\520\mysite>python manage.py shell
Python 3.7.7 (tags/v3.7.7:d7c567b08f, Mar 10 2020, 10:41:24) [MSC v.1900 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
(InteractiveConsole)
>>> from myapp.models import Book
>>> b1 = Book.objects.get(id=1)
>>> b1.delete()
(1, {'myapp.Book': 1})
>>> bs = Book.objects.all()
>>> bs
<QuerySet [<Book: 书名：django_出版社：清华大学出版社_价格：33.00_市场价：750.00>, <Book: 书名：jquery_出版社：机械工业 出版社_价格：99.00_市场价：85.00>, <Book: 书名：linux_出版社：机械工业出版社_价格：80.00_市场价：65.00>, <Book: 书名：html5_出版社：清华大学出版社_价格：1.00_市场价：105.00>]>
>>>

为Book类添加is_active字段，

# models.py
from django.db import modelsclass Book(models.Model):title = models.CharField(max_length=50, default="", verbose_name="书名", unique=True)pub = models.CharField(max_length=100, default="", verbose_name="出版社")price = models.DecimalField(max_digits=7, decimal_places=2, default=999, verbose_name="价格")market_price = models.DecimalField(max_digits=7, decimal_places=2, default=9999, verbose_name="零售价")is_active = models.BooleanField(verbose_name="是否活跃", default=True)class Meta:db_table = "book"def __str__(self):return "书名：{}_出版社：{}_价格：{}_市场价：{}".format(self.title, self.pub, self.price, self.market_price)

C:\Users\520\mysite>python manage.py makemigrations
Migrations for 'myapp':myapp\migrations\0005_book_is_active.py- Add field is_active to bookC:\Users\520\mysite>python manage.py migrate
Operations to perform:Apply all migrations: admin, auth, contenttypes, myapp, sessions
Running migrations:Applying myapp.0005_book_is_active... OK

C:\Users>cd..C:\>cd program files\mysql\mysql server 8.0\binC:\Program Files\MySQL\MySQL Server 8.0\bin>mysql -uroot -p
Enter password: ****
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 89
Server version: 8.0.25 MySQL Community Server - GPLCopyright (c) 2000, 2021, Oracle and/or its affiliates.Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.mysql> use mysite;
Database changed
mysql> show tables;
+----------------------------+
| Tables_in_mysite           |
+----------------------------+
| auth_group                 |
| auth_group_permissions     |
| auth_permission            |
| auth_user                  |
| auth_user_groups           |
| auth_user_user_permissions |
| author                     |
| book                       |
| django_admin_log           |
| django_content_type        |
| django_migrations          |
| django_session             |
+----------------------------+
12 rows in set (0.01 sec)mysql> desc book;
+--------------+--------------+------+-----+---------+----------------+
| Field        | Type         | Null | Key | Default | Extra          |
+--------------+--------------+------+-----+---------+----------------+
| id           | bigint       | NO   | PRI | NULL    | auto_increment |
| title        | varchar(50)  | NO   | UNI | NULL    |                |
| price        | decimal(7,2) | NO   |     | NULL    |                |
| market_price | decimal(7,2) | NO   |     | NULL    |                |
| pub          | varchar(100) | NO   |     | NULL    |                |
| is_active    | tinyint(1)   | NO   |     | NULL    |                |
+--------------+--------------+------+-----+---------+----------------+
6 rows in set (0.00 sec)mysql> select * from book;
+----+--------+-------+--------------+----------------+-----------+
| id | title  | price | market_price | pub            | is_active |
+----+--------+-------+--------------+----------------+-----------+
|  2 | django | 33.00 |       750.00 | 清华大学出版社 |         1 |
|  3 | jquery | 99.00 |        85.00 | 机械工业出版社 |         1 |
|  4 | linux  | 80.00 |        65.00 | 机械工业出版社 |         1 |
|  5 | html5  |  1.00 |       105.00 | 清华大学出版社 |         1 |
+----+--------+-------+--------------+----------------+-----------+
4 rows in set (0.01 sec)mysql>

1、路径转换器方式，path匹配URL，同时视图里传参
2、查询字符串方式，在HTML页面里设置a标签地址
https://docs.djangoproject.com/zh-hans/3.1/topics/http/urls/#path-converters

from django.contrib import admin
from django.urls import path, includeurlpatterns = [path('admin/', admin.site.urls),path("bookstore/", include("myapp.urls"))
]

from django.urls import path
from . import viewsurlpatterns = [path("all_book", views.all_book),path("update_book/<int:book_id>", views.update_book),path("delete_book", views.delete_book)
]

views.py

from django.shortcuts import render
from django.http import HttpResponse, HttpResponseRedirect
from .models import Book# Create your views here.
def all_book(request):# all_book = Book.objects.all()all_book = Book.objects.filter(is_active=True)return render(request, "myapp/abook.html", locals())def update_book(request, book_id):# 查try:book = Book.objects.get(id=book_id, is_active=True)except Exception as e:print("update book error is {}".format(e))return HttpResponse("book {} does not exist".format(book_id))if request.method == "GET":return render(request, "myapp/update_book.html", locals())elif request.method == "POST":price = request.POST['price']market_price = request.POST['market_price']# 改book.price = pricebook.market_price = market_price# 存book.save()return HttpResponseRedirect("/bookstore/all_book")  # 注意：相对地址def delete_book(request):# 通过获取查询字符串book_id拿到要删除的book的idbook_id = request.GET.get("book_id")if not book_id:return HttpResponse("请求异常")try:book = Book.objects.get(id=book_id, is_active=True)except Exception as e:print("--error-{}".format(e))return HttpResponse("--the book id is error")# 将其is_active该为Falsebook.is_active = Falsebook.save()# 302跳转到all_bookreturn HttpResponseRedirect("/bookstore/all_book")

abook.py

<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><title>查看所有书籍</title>
</head>
<body>
<table border="1"><tr><th>id</th><th>title</th><th>pub</th><th>price</th><th>market_price</th><th>op</th></tr><tr>{% for book in all_book %}<tr><td>{{ book.id }}</td><td>{{ book.title }}</td><td>{{ book.pub }}</td><td>{{ book.price }}</td><td>{{ book.market_price }}</td><td><a href="/bookstore/update_book/{{ book.id }}">更新</a><a href="/bookstore/delete_book?book_id={{ book.id }}">删除</a></td></tr>{% endfor %}</tr>
</table></body>
</html>

mysql> select * from book;
+----+--------+-------+--------------+----------------+-----------+
| id | title  | price | market_price | pub            | is_active |
+----+--------+-------+--------------+----------------+-----------+
|  2 | django | 33.00 |       750.00 | 清华大学出版社 |         1 |
|  3 | jquery | 99.00 |        85.00 | 机械工业出版社 |         1 |
|  4 | linux  | 80.00 |        65.00 | 机械工业出版社 |         1 |
|  5 | html5  |  1.00 |       105.00 | 清华大学出版社 |         1 |
+----+--------+-------+--------------+----------------+-----------+
4 rows in set (0.01 sec)# 删除之后，is_active字段变化mysql> select * from book;
+----+--------+-------+--------------+----------------+-----------+
| id | title  | price | market_price | pub            | is_active |
+----+--------+-------+--------------+----------------+-----------+
|  2 | django | 33.00 |       750.00 | 清华大学出版社 |         1 |
|  3 | jquery | 99.00 |        85.00 | 机械工业出版社 |         1 |
|  4 | linux  | 80.00 |        65.00 | 机械工业出版社 |         0 |
|  5 | html5  |  1.00 |       105.00 | 清华大学出版社 |         0 |
+----+--------+-------+--------------+----------------+-----------+
4 rows in set (0.00 sec)mysql>

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