Django learning record: Use ORM to operate MySQL database and complete data addition, deletion, modification and query

Database operations

MySQL database+pymysql

Django development and operation of the database are simpler, and an ORM framework is provided internally.

Install third-party modules

pip install mysqlclient

What ORM can do:

1. Create, modify, and delete tables in the database (without writing SQL statements). [Unable to create database]

2. Manipulate the data in the table (no need to write SQL statements).

1. Create your own database

1) Start the MySQL service

2) Bring your own tools to create a database

2. Django connects to the database

Configure and modify in the setting.py file: the local mysql database is connected here

DATABASES = {
    
    
    'default': {
    
    
        'ENGINE': 'django.db.backends.mysql',
        'NAME':  'dbname', # 数据库名字
        'USER':  'root',
        'PASSWORD':  'xxxxxx',
        'HOST':  'localhost',
        'PORT':  3306,
    }
}

3. Django operation table

create table
Delete table
Modify table

Create table: In models.py file:

class UserInfo(models.Model):
    name = models.CharField(max_length=32) # charfield 字符串类型
    password = models.CharField(max_length=64)
    age = models.IntegerField() # IntegerField 整数类型

Equivalent to running in MySQL

create table app01_userinfo(
    id bigint auto_increment primary key,
    name varchar(32),
    password varchar(64),
    age int
);

Then, execute the commands sequentially in the terminal: (Note: the app needs to be registered in advance.)

python manage.py makemigrations
python manage.py migrate

You can create the app01_userinfo file in mysql

Insert image description here

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

Enter a value manually
Set default value
```
size = models.IntegerField(default=2)
```

Allow empty

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

If you want to adjust the table structure during development:

Just operate the class in the models.py file.

Execute the command in the terminal

python manage.py makemigrations
python manage.py migrate

Addition, deletion, modification and query of data

from app01 import models

1. Create new

    # ###新建###
    models.Department.objects.create(title="销售部")
    models.Department.objects.create(title="IT部")
    models.Department.objects.create(title="运营部")
    models.UserInfo.objects.create(name="dumpling", password="123", age="22")
    models.UserInfo.objects.create(name="noodles", password="111", age="20")

2. Delete

# ###删除###
    models.UserInfo.objects.filter(id=3).delete()
    models.Department.objects.all().delete()

3. View (obtain data)

    ###获取数据###
    #获取的是列表，列表是一行一行的数据
    #data_list = [行（对象） 行 行]   QuerySet类型
    data_list = models.UserInfo.objects.all()
    for obj in data_list:
            print(obj.id, obj.name, obj.password, obj.age)

    # 寻找id=1的数据。data_list = [对象，],这个方法取到的还是QuerySet类型
    data_list = models.UserInfo.objects.filter(id=1)
    # 取对象中的第一个，这个方法就能直接将第一行对象取出来
    row_obj = models.UserInfo.objects.filter(id=1).first()
    print(row_obj.id, row_obj.name, row_obj.password, row_obj.age)

4. Update

	models.UserInfo.objects.all().update(password=999)
    models.UserInfo.objects.filter(id=2).update(age=999)