設計資料庫和表結構是做網站的基礎。在Django中，不需要通過SQL語句直接跟資料庫打交道，而是完全用Python的類來建立資料模型，之後交給Django完成建立資料庫的操作。

資料模型類

資料模型類需要在 應用目錄 下的 models.py 檔案中編寫

編寫資料模型

• 下面的程式碼演示了在 models.py 中定義了一個部落格文章的類

from django.db import models
from django.utils import timezone
from django.contrib.auth.models import User


# Create your models here.
class BlogArticles(models.Model):  # Django中的資料模型類都繼承自 django.db.models.Model類
    # 欄位 title 的屬性為 CharField 型別，並且引數長度為 300
    title = models.CharField(max_length=300)
    """
    欄位 author 使用 ForeignKey 規定了部落格文章和使用者之間的關係：一個使用者對應多篇文章
    models.CASCADE 表示級聯刪除
    related_name="blog_posts" 表示允許User類的例項以 "blog_posts" 屬性反向查詢到BlogArticles類的例項
    """
    author = models.ForeignKey(User, on_delete=models.CASCADE, related_name="blog_posts")
    body = models.TextField()
    publish = models.DateTimeField(default=timezone.now)

    """
    ordering = ("-publish",) 規定BlogArticles類的例項按 publish 欄位值倒序顯示
    """
    class Meta:
        ordering = ("-publish",)

    """
    重寫父類的方法，使得當使用 str()函式轉換該類的例項為字串時，返回 title 屬性的值
    """
    def __str__(self):
        return self.title
 

根據資料模型建立資料庫表

1. 建立資料庫表文件

E:\PycharmProjects\demosite>python manage.py makemigrations
Migrations for 'blog':
  blog\migrations\0002_auto_20190720_1919.py
    - Alter field publish on blogarticles

2. 上面執行結果的提示資訊中，告訴我們在 blog/migrations 目錄中建立了一個 BlogArticles模型，模型編號為 0001。可以輸入以下命令檢視相對應的SQL語句:

E:\PycharmProjects\demosite>python manage.py sqlmigrate blog 0001
System check identified some issues:

WARNINGS:
blog.BlogArticles.publish: (fields.W161) Fixed default value provided.
        HINT: It seems you set a fixed date / time / datetime value as default for this field. This may not be what you want. If you want to have the current date as default, use `django.utils.timezone.now`
BEGIN;
--
-- Create model BlogArticles
--
CREATE TABLE "blog_blogarticles" ("id" integer NOT NULL PRIMARY KEY AUTOINCREMENT, "title" varchar(300) NOT NULL, "body" text NOT NULL, "publish" datetime NOT NULL, "author_id" integer NOT NULL REFERENCES "auth_user" ("id") DEFERRABLE INITIALLY DEFERRED);
CREATE INDEX "blog_blogarticles_author_id_ed798e23" ON "blog_blogarticles" ("author_id");
COMMIT;

 

在資料庫中表名格式為：小寫的應用名稱_小寫的類名稱

3. 建立資料庫

(demosite) E:\PycharmProjects\demosite>python manage.py migrate
System check identified some issues:

WARNINGS:
blog.BlogArticles.publish: (fields.W161) Fixed default value provided.
        HINT: It seems you set a fixed date / time / datetime value as default for this field. This may not be what you want. If you want to have the current date as default, use `django.utils.timezone.now`
Operations to perform:
  Apply all migrations: admin, auth, blog, contenttypes, sessions
Running migrations:
  Applying contenttypes.0001_initial... OK
  Applying auth.0001_initial... OK
  Applying admin.0001_initial... OK
  Applying admin.0002_logentry_remove_auto_add... OK
  Applying admin.0003_logentry_add_action_flag_choices... OK
  Applying contenttypes.0002_remove_content_type_name... OK
  Applying auth.0002_alter_permission_name_max_length... OK
  Applying auth.0003_alter_user_email_max_length... OK
  Applying auth.0004_alter_user_username_opts... OK
  Applying auth.0005_alter_user_last_login_null... OK
  Applying auth.0006_require_contenttypes_0002... OK
  Applying auth.0007_alter_validators_add_error_messages... OK
  Applying auth.0008_alter_user_username_max_length... OK
  Applying auth.0009_alter_user_last_name_max_length... OK
  Applying auth.0010_alter_group_name_max_length... OK
  Applying auth.0011_update_proxy_permissions... OK
  Applying blog.0001_initial... OK
  Applying sessions.0001_in