I want to create database model in django and define a foreign key. All the example I see in internet have following syntax.

```
attr = models.ForeignKey(Entity) 

```

However I want a foreign key to be linked with single attribute from another entity and not the whole entity.

I have following models:

```
class User(models.Model):
user_id = models.PositiveIntegerField(primary_key=True)
password = models.CharField(max_length=20)
email = models.EmailField()
........

class ContentItem(models.Model):
content_id = models.PositiveIntegerField(primary_key=True)
title = models.CharField(max_length=100)
description = models.TextField()
.........
author_id = models.ForeignKey(User, on_delete= models.CASCADE)

```

Here, I want ContentItem.author\_id to be foreign key for User.user\_id and not the whole User model. While entering value for author\_id, I simply want to enter plain id (1,2,3) and not all the instance of User

Sorry if the question is very general and thanks in advance