Python 3.x 在django中使用default和foreignkey模型

我正在做一个django项目，我有3个模型 -类别 -子类别 -产品

子类别是类别的外键，而产品是类别和产品的外键

运行迁移时，会出现以下错误：

django.db.utils.IntegrityError:主键为“5”的表“shop\u product”中的行具有无效外键：shop\u product.subcategory\u id包含的值“1”在shop\u subcategory.id中没有相应的值。

型号.py

from django.db import models
from django.urls import reverse
from ckeditor.fields import RichTextField
# Create your models here.


class Category(models.Model):
    name = models.CharField(max_length=200, db_index=True)
    slug = models.SlugField(max_length=200, db_index=True)

    class Meta:
        ordering = ('name',)
        verbose_name = 'category'
        verbose_name_plural = "categories"

    def __str__(self):
        return self.name

    def get_absolute_url(self):
        return reverse('shop:product_list_by_category', args=[self.slug])


class Subcategory(models.Model):
    category = models.ForeignKey(Category, related_name='subcategories', on_delete=models.CASCADE)
    name = models.CharField(max_length=200, db_index=True)
    slug = models.SlugField(max_length=200, db_index=True)

    class Meta:
        ordering = ('name',)
        verbose_name = 'subcategory'
        verbose_name_plural = 'subcategories'

    def __str__(self):
        return self.name


class Product(models.Model):
    name = models.CharField(max_length=200, db_index=True)
    slug = models.SlugField(max_length=200, db_index=True)
    description = RichTextField(blank=True, null=True)
    subcategory = models.ForeignKey(Subcategory, related_name='product', on_delete=models.CASCADE, null=True, default=1)
    category = models.ForeignKey(Category, related_name='products', on_delete=models.CASCADE)
    image = models.ImageField(upload_to='products/%Y/%m/%d', blank=True)
    price = models.DecimalField(max_digits=10, decimal_places=2)
    available = models.BooleanField(default=True)
    created = models.DateTimeField(auto_now_add=True)
    updated = models.DateTimeField(auto_now=True)

    class Meta:
        ordering = ('name',)
        index_together = (('id', 'slug'),)

    def __str__(self):
        return self.name

    def get_absolute_url(self):
        return reverse('shop:product_detail', args=[self.id, self.slug])

终端输出

python3 manage.py migrate
Operations to perform:
  Apply all migrations: admin, auth, contenttypes, coupons, orders, sessions, shop
Running migrations:
  Applying shop.0002_auto_20201103_1603...Traceback (most recent call last):
  File "manage.py", line 22, in <module>
    main()
  File "manage.py", line 18, in main
    execute_from_command_line(sys.argv)
  File "/home/kolawole/Desktop/myshop/env/lib/python3.8/site-packages/django/core/management/__init__.py", line 401, in execute_from_command_line
    utility.execute()
  File "/home/kolawole/Desktop/myshop/env/lib/python3.8/site-packages/django/core/management/__init__.py", line 395, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/home/kolawole/Desktop/myshop/env/lib/python3.8/site-packages/django/core/management/base.py", line 330, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/home/kolawole/Desktop/myshop/env/lib/python3.8/site-packages/django/core/management/base.py", line 371, in execute
    output = self.handle(*args, **options)
  File "/home/kolawole/Desktop/myshop/env/lib/python3.8/site-packages/django/core/management/base.py", line 85, in wrapped
    res = handle_func(*args, **kwargs)
  File "/home/kolawole/Desktop/myshop/env/lib/python3.8/site-packages/django/core/management/commands/migrate.py", line 243, in handle
    post_migrate_state = executor.migrate(
  File "/home/kolawole/Desktop/myshop/env/lib/python3.8/site-packages/django/db/migrations/executor.py", line 117, in migrate
    state = self._migrate_all_forwards(state, plan, full_plan, fake=fake, fake_initial=fake_initial)
  File "/home/kolawole/Desktop/myshop/env/lib/python3.8/site-packages/django/db/migrations/executor.py", line 147, in _migrate_all_forwards
    state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
  File "/home/kolawole/Desktop/myshop/env/lib/python3.8/site-packages/django/db/migrations/executor.py", line 229, in apply_migration
    migration_recorded = True
  File "/home/kolawole/Desktop/myshop/env/lib/python3.8/site-packages/django/db/backends/sqlite3/schema.py", line 35, in __exit__
    self.connection.check_constraints()
  File "/home/kolawole/Desktop/myshop/env/lib/python3.8/site-packages/django/db/backends/sqlite3/base.py", line 343, in check_constraints
    raise IntegrityError(
django.db.utils.IntegrityError: The row in table 'shop_product' with primary key '5' has an invalid foreign key: shop_product.subcategory_id contains a value '1' that does not have a corresponding value in shop_subcategory.id.

python3 manage.py迁移
要执行的操作：
应用所有迁移：管理、身份验证、内容类型、优惠券、订单、会话、商店
运行迁移：
正在应用shop.0002_auto_20201103_1603…回溯（最近一次呼叫最后一次）：
文件“manage.py”，第22行，在
main（）
文件“manage.py”，第18行，主
从命令行（sys.argv）执行命令
文件“/home/kolawole/Desktop/myshop/env/lib/python3.8/site packages/django/core/management/__init__;.py”，第401行，从命令行执行
utility.execute（）
文件“/home/kolawole/Desktop/myshop/env/lib/python3.8/site packages/django/core/management/_init__.py”，第395行，在execute中
self.fetch_命令（子命令）。从_argv（self.argv）运行_
文件“/home/kolawole/Desktop/myshop/env/lib/python3.8/site-packages/django/core/management/base.py”，第330行，运行于
self.execute（*args，**cmd_选项）
文件“/home/kolawole/Desktop/myshop/env/lib/python3.8/site packages/django/core/management/base.py”，第371行，在execute中
输出=self.handle（*args，**选项）
文件“/home/kolawole/Desktop/myshop/env/lib/python3.8/site packages/django/core/management/base.py”，第85行，包装
res=句柄函数（*args，**kwargs）
handle中的文件“/home/kolawole/Desktop/myshop/env/lib/python3.8/site packages/django/core/management/commands/migrate.py”，第243行
post\u migrate\u state=executor.migrate(
文件“/home/kolawole/Desktop/myshop/env/lib/python3.8/site packages/django/db/migrations/executor.py”，第117行，在migrate中
状态=self.\u迁移\u所有\u转发（状态，计划，完整计划，假=假，假首字母=假首字母）
文件“/home/kolawole/Desktop/myshop/env/lib/python3.8/site packages/django/db/migrations/executor.py”，第147行，全部向前迁移
state=self.apply\u迁移（state，migration，false=false，false\u initial=false\u initial）
文件“/home/kolawole/Desktop/myshop/env/lib/python3.8/site packages/django/db/migrations/executor.py”，第229行，在apply_migration中
迁移记录=真
文件“/home/kolawole/Desktop/myshop/env/lib/python3.8/site packages/django/db/backends/sqlite3/schema.py”，第35行，在退出时__
self.connection.check_约束（）
文件“/home/kolawole/Desktop/myshop/env/lib/python3.8/site packages/django/db/backends/sqlite3/base.py”，第343行，检查约束
提高积分误差(
django.db.utils.IntegrityError:主键为“5”的表“shop_product”中的行具有无效外键：shop_product.subcategory_id包含的值“1”在shop_subcategory.id中没有相应的值。

我使用python 3.8.5和django 3.1.2

---

有什么有用的建议吗？谢谢。

您已经在Product.subcategory foreignkey options中定义了default=1。 似乎子类别中没有id等于1的条目。 您应该在迁移之前提供一个条目，或者更改id以引用现有子类别，或者删除默认选项