Question

我有一个包含9个表的MySQL数据库。它们都以某种方式相关，但我无法连接外键。例如，当我尝试python manage.py migrate时，我的两个表格出现错误：

class Release(models.Model):
     release_ID = models.CharField(max_length=25, primary_key =True)
     releaseversion = models.CharField(max_length=25)
     model_ID = models.ForeignKey(Model, on_delete=models.CASCADE) #comes from Model class

class Subrelease(models.Model):
     subrelease_ID = models.CharField(max_length=25)
     release_ID = models.ForeignKey('Release', blank =True) #comes from Release class 
     subreleaseversion = models.CharField(max_length=25)

如何从类Release发出主键，release_ID也是类Subrelease中的ForeignKey release_ID？任何帮助将非常感激。谢谢。

运行迁移后，我在cmd中得到了这个：

django.db.utils.InternalError: (1829, "Cannot drop column 'id': needed in a foreign 
    key constraint 'app_subrel_release_ID_id_8e08450_fk_app_release_id' of table
    'db.app_subrelease'")

更新这好/可以吗？迁移到DB时，我没有任何错误？

class Release(models.Model):
     #release_ID = models.CharField(max_length=25, primary_key =True)THIS WILL BE OUR PRIMARY KEY MADE BY DJANGO
     releaseversion = models.CharField(max_length=25)
     model = models.ForeignKey(Model, on_delete=models.CASCADE) #comes from Model class model_ID



class Subrelease(models.Model):
     #subrelease_ID = models.CharField(max_length=25) THIS WILL BE OUR PRIMARY KEY MADE BY DJANGO
     release = models.ForeignKey(Release, on_delete=models.CASCADE ) #comes from Release class release_ID
     subreleaseversion = models.CharField(max_length=25)

Answer 1

您可以尝试使用to_field和db_column选项。

class B(models.Model):
    name = models.ForeignKeyField(A, to_field="name", db_column="name")

创建外键后，您可以按如下方式访问值和相关实例：

>>> b = B.objects.get(id=1)
>>> b.name_id # the value stored in the 'name' database column
>>> b.name # the related 'A' instance

参考： this answer

Django主键充当外键

1 个答案: