Django framework 003: the connection between orm and MySQL database and the record of stepping on the pit

 Hello everyone, I am the blogger of csdn: lqj_ myself

This is my personal blog homepage:

lqj_My blog_CSDN blog-WeChat applet, front-end, python field blogger lqj_I am good at WeChat applet, front-end, python, etc. https://blog.csdn.net/lbcyllqj?spm=1011.2415 .3001.5343 Bilibili welcome attention:Xiao Miao Develop

Xiaomiao Develop's personal space-Xiaomiao Develop personal homepage-哔哩哔哩Video

This article mainly talks about: Quick start, pythonweb development Django framework

Table of contents

mysqlclient module

ORM

1. Manually create the database

Start your own mysql service

 cmd command window to create a database

2. Djngo connects to the database

Configure and modify in the setting.py file.

3. Make sure the app is registered

4. Djngo operation table (the naming method of the automatically created table: registered app name + class name "UserInfo")

Write in the models.py file (demonstration code: create a data structure in the app01_userinfo table:

name，password，age）

At this point, there may be errors that may occur

problem solved

data table in database

 The data structure of the data table

Delete table/delete data in table

Modify table data structure

Summarize

---

mysqlclient module

Django supports the mysqlclient module, through which to connect to the mysql database greatly saves some tedious operations that we use in the pymysql module library.

pip install mysqlclient 

ORM

ORM can help us do two things:

1. Create, modify, and delete tables in the database (no need to write sql statements) but [the database cannot be created, the database must be created manually in mysql]

2. Manipulate the data in the table (no need to write sql statement)

so:

1. Manually create the database

Start your own mysql service

Method 1: Enter the following command into mysql:

net start 你的mysql名字

Method 2: Enter "Task Manager" > right click to start

 cmd command window to create a database

create database 数据库名字;

2. Djngo connects to the database

Configure and modify in the setting.py file.

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.mysql',
        'NAME': '数据库名字', 
        'USER': 'mysql用户名',
        'PASSWORD': 'mysql密码器',
        'HOST': '127.0.0.1',  # 安装MySQL数据库的机器
        'PORT': 3306  # 端口
    }
}

3. Make sure the app is registered

Viewed in setting.py (app01 has been registered)

INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'app01.apps.App01Config'
]

4. Djngo operation table (the naming method of the automatically created table: registered app name + class name "UserInfo")

Write in the models.py file (demonstration code: create a data structure in the app01_userinfo table:

name，password，age）

from django.db import models


class UserInfo(models.Model):
    name = models.CharField(max_length=32)
    password = models.CharField(max_length=64)
    age = models.IntegerField()

Immediately after writing, in the command window in pycharm, enter the command in the root directory of the Django file:

python manage.py makemigrations

At this time, observe whether the py file is automatically added under the migrations folder (as shown in the figure below:)

Then, enter the command:

python manage.py migrate

At this point, there may be errors that may occur

django.db.utils.NotSupportedError: MySQL 5.7 or later is required

This is caused by the incompatibility between the installed Django and mysql versions.

problem solved

1. Lower the version of our Django module library

2. Innovatively install a mysql database above version 8

After solving the compatibility problem, re-run the command: python manage.py migrate

data table in database

 The data structure of the data table

Delete table/delete data in table

Comment or delete the class (such as: userinfo class)/data structure (such as: name field) that you want to delete in the models.py file, and re-execute the following command

python manage.py makemigrations
python manage.py migrate

Modify table data structure

When adding a new column to a table, since there may already be data in the existing list, the new column must specify the data corresponding to the new column:

1. Manually enter a value

set default

age = models.IntegerField(default=2)

Allow empty

age = models.IntegerField(null=True,blank=True)

Summarize

In the future, if you want to adjust the table structure during development:

Just operate in the models.py file.

python manage.py makemigrations
python manage.py migrate