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Django ORM

  • Comprehensive guide to Django ORM including QuerySets, data filtering, and performing CRUD operations.

  • What is Django ORM?

    Django ORM (Object Relational Mapping) allows us to interact with the database using Python code instead of SQL queries.

    ORM converts:

    Python code ↔ SQL queries ↔ Database

    Why Use Django ORM?

    • No SQL knowledge required

    • Database-independent

    • Secure (prevents SQL injection)

    • Clean and readable code

    CRUD Operations in Django ORM

    CRUD stands for:

    • Create

    • Read

    • Update

    • Delete

We will use this model for examples: 

class Student(models.Model):
    name = models.CharField(max_length=100)
    email = models.EmailField()
    age = models.IntegerField()
    is_active = models.BooleanField(default=True)

  • CREATE (Insert Data)

    Using save()

Insert Record Using save()

Creates an object and saves it to the database. 

student = Student(
    name="Hinal",
    email="hinal@gmail.com",
    age=22
)
student.save()

Using objects.create()

Insert Record Using create() 

Student.objects.create(
    name="Amit",
    email="amit@gmail.com",
    age=24
)

  • READ (Fetch Data)

    Fetch All Records

Fetch All Students 

students = Student.objects.all()

Fetch Single Student 

student = Student.objects.get(id=1)

Fetch First & Last Record 

Student.objects.first()
Student.objects.last()

Update Student Record 

student = Student.objects.get(id=1)
student.age = 23
student.save()

Update Multiple Records 

Student.objects.filter(is_active=True).update(age=25)

Delete Single Record 

student = Student.objects.get(id=1)
student.delete()

Delete Multiple Records 

Student.objects.filter(is_active=False).delete()

  • QuerySets in Django ORM

    What is a QuerySet?

    A QuerySet is a collection of database records.

    students = Student.objects.all()

    QuerySets are lazy → database is hit only when needed.

    Filtering Data (WHERE Clause)

filter()

Filter Students by Age 

students = Student.objects.filter(age=22)

exclude()

Exclude Records 

students = Student.objects.exclude(age=22)

Multiple Conditions 

Student.objects.filter(age=22, is_active=True)

  • Field Lookups (Advanced Filters)

greater than / less than 

Student.objects.filter(age__gt=20)
Student.objects.filter(age__lt=25)

contains / icontains 

Student.objects.filter(name__contains="hi")
Student.objects.filter(name__icontains="hi")

in lookup 

Student.objects.filter(age__in=[20, 22, 24])

startswith / endswith 

Student.objects.filter(name__startswith="H")
Student.objects.filter(email__endswith="gmail.com")

  • Ordering & Limiting Data

order_by()

Order Students 

Student.objects.order_by('age')      # Ascending
Student.objects.order_by('-age')     # Descending

Limit Records 

Student.objects.all()[:5]
  • Counting & Existence

count() 

Student.objects.count()

exists() 

Student.objects.filter(email="test@gmail.com").exists()
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