django abstract models versus regular inheritance

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I actually want to know the difference between a model class that
inherits from a django abstract class (Meta: abstract = True) and a
plain Python class that inherits from say, ‘object’ (and not
models.Model).

Django will only generate tables for subclasses of models.Model, so the former…

class User(models.Model):
   first_name = models.CharField(max_length=255)

   def get_username(self):
       return self.username

   class Meta:
       abstract = True

class Employee(User):
   title = models.CharField(max_length=255)

…will cause a single table to be generated, along the lines of…

CREATE TABLE myapp_employee
(
    id         INT          NOT NULL AUTO_INCREMENT,
    first_name VARCHAR(255) NOT NULL,
    title      VARCHAR(255) NOT NULL,
    PRIMARY KEY (id)
);

…whereas the latter…

class User(object):
   first_name = models.CharField(max_length=255)

   def get_username(self):
       return self.username

class Employee(User):
   title = models.CharField(max_length=255)

…won’t cause any tables to be generated.

You could use multiple inheritance to do something like this…

class User(object):
   first_name = models.CharField(max_length=255)

   def get_username(self):
       return self.username

class Employee(User, models.Model):
   title = models.CharField(max_length=255)

…which would create a table, but it will ignore the fields defined in the User class, so you’ll end up with a table like this…

CREATE TABLE myapp_employee
(
    id         INT          NOT NULL AUTO_INCREMENT,
    title      VARCHAR(255) NOT NULL,
    PRIMARY KEY (id)
);

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