Django ORM vs SQLAlchemy

Django ORM vs SQLAlchemy in Details

Both are Object Relational Mappers (ORMs) in Python, but they serve different use cases and philosophies.

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✅ Django ORM

• Comes built-in with Django.
• Opinionated and tightly integrated with Django’s ecosystem (models, admin, forms, views).
• Uses a simpler, declarative style for defining models.
• Prioritizes developer productivity and “Django way of doing things”.

Example (Django ORM)

# models.py
from django.db import models

class Customer(models.Model):
    name = models.CharField(max_length=100)
    is_active = models.BooleanField(default=True)

# Query
active_customers = Customer.objects.filter(is_active=True)

👉 Easy to read, quick to build. 👉 Best if you are building a Django app (don’t reinvent the wheel).

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✅ SQLAlchemy

• Independent ORM (not tied to any web framework).

• Used in Flask, FastAPI, Pyramid, or even standalone scripts.

• Offers two layers:

  1. Core → Low-level SQL builder.
  2. ORM → Higher-level object mapping.

• More flexible and powerful, but requires more setup.

Example (SQLAlchemy ORM)

from sqlalchemy import Column, Integer, String, Boolean, create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker

Base = declarative_base()

class Customer(Base):
    __tablename__ = "customers"
    id = Column(Integer, primary_key=True)
    name = Column(String(100))
    is_active = Column(Boolean, default=True)

# DB setup
engine = create_engine("sqlite:///test.db")
Session = sessionmaker(bind=engine)
session = Session()

# Query
active_customers = session.query(Customer).filter(Customer.is_active == True).all()

👉 More verbose, but extremely flexible (you can drop to raw SQL easily). 👉 Best if you want fine control over queries or use frameworks other than Django.

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🔥 Key Differences

Feature	Django ORM	SQLAlchemy
Integration	Built into Django only	Framework-agnostic (Flask, FastAPI)
Ease of Use	Easier, less boilerplate	More verbose, but powerful
Flexibility	Limited (Django conventions)	Very flexible (Core + ORM)
Learning Curve	Easy for beginners	Steeper learning curve
Migrations	Built-in with makemigrations	Needs Alembic
Performance	Good for typical web apps	Optimized for complex queries
Use Case	Quick web apps with Django	Complex, non-Django projects, microservices

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🚀 Which one is better?

👉 Use Django ORM if

• You are working on a Django project.
• You value speed of development over flexibility.
• You want everything (ORM, admin, migrations, forms) already integrated.

👉 Use SQLAlchemy if

• You are using Flask, FastAPI, or microservices.
• You need complex queries and DB-specific optimizations.
• You want fine-grained control over SQL and schema evolution.

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🔑 In short:

• Django ORM = easy, integrated, fast development (but less flexible).
• SQLAlchemy = powerful, flexible, framework-agnostic (but more boilerplate).