This is an additional option within the **Meta class**, utilized for establishing certain constraints on the model. Implementing the `unique=True` option on a field effectively acts as a constraint.

#### UniqueConstraint
Ensures that the combination of specified field values is unique across the database table.
``` python
from django.db import models
from django.db.models import UniqueConstraint

class Book(models.Model):
    title = models.CharField(max_length=100)
    genre = models.ForeignKey(Genre, on_delete=models.CASCADE)
    author = models.ForeignKey(Author, on_delete=models.CASCADE)

    class Meta:
        constraints = [
            UniqueConstraint(fields=["title", "genre"], name="unique_book_titles_per_genre")
        ]
```
In this example, the `UniqueConstraint` ensures that no two books in the same genre have the same title.

#### CheckConstraint
Ensures that certain conditions hold true for the data in the database.

Suppose you want to ensure that the author's age is always greater than 18.
``` python
from django.db.models import CheckConstraint, Q

class Author(models.Model):
    name = models.CharField(max_length=100)
    age = models.IntegerField()

    class Meta:
        constraints = [
            CheckConstraint(check=Q(age__gt=18), name="age_greater_than_18")
        ]
```


What is the purpose of the unique attribute in a Django model field?

What is the primary use of UniqueConstraint in Django's Meta class?

What does CheckConstraint do in Django models?

Learn how to build applications using the Django ORM framework. This is the next step in expanding your knowledge of Django development.

A quick overview of the Django ORM. One of the advantages of Django is the Django ORM.

You will learn about Django's robust modeling system, including field data types for precise database structuring. The section also covers migrations for seamless schema updates and the powerful admin interface, providing an intuitive way to manage your application's data.

This essential section is your treasure map for navigating Create, Read, Update, and Delete (CRUD) operations. Effortlessly craft queries to add new records, fetch and explore data with finesse, seamlessly update existing records, and confidently delete what's no longer needed. Each example is a key, unlocking the power and elegance of Django ORM. 🌟🔍💻🚀

Explore the intricate world of database relationships in Django! This section delves into the core concepts of Many-to-One, One-to-One, and Many-to-Many relationships. Learn how to effectively model real-world scenarios in your database using Django's powerful ORM, with clear examples and practical use-cases to guide you.

After this section, you will be able to master Django's field lookups, Q and F objects for advanced queries, and Aggregation and Annotation for data summarization. You'll also learn techniques to minimize database hits, addressing the N+1 problem, and effectively using select and prefetch related.

This section delves into advanced Django concepts, including the Meta class for model customization, the implementation of constraints for data integrity, the basics of transactions for ensuring database consistency, and an overview of the User model, a core component for handling user authentication and permissions in Django applications.

Django ORM Ninja: Advanced Techniques for Developers

Constrains

UniqueConstraint

CheckConstraint

1. What is the purpose of the unique attribute in a Django model field?

2. What is the primary use of UniqueConstraint in Django's Meta class?

3. What does CheckConstraint do in Django models?