An ORM (Object-Relational Mapper) lets you work with a SQL database using Python objects.

Instead of writing SQL like:

SELECT id, username FROM users WHERE id = 1;

SELECT id, username FROM users WHERE id = 1;

You write Python like:

user = User.query.get(1)

user = User.query.get(1)

What an ORM gives you

• Python classes represent tables
• Instances represent rows
• Methods/queries generate SQL
• Safe parameter binding (helps prevent SQL injection)
• Relationships (foreign keys) become Python attributes

Tradeoffs

ORMS are great, but not magic:

• You still need to understand SQL concepts (indexes, joins, transactions)
• Bad queries are still possible (N+1 query problem)
• For complex reporting, raw SQL can be clearer

Flask + SQLAlchemy

In Flask apps, a common stack is:

• Flask-SQLAlchemy: app integration + dbdb helper
• SQLAlchemy: the ORM engine

You’ll define models and query them, but it helps to keep SQL fundamentals in mind.

🧪 Try It Yourself

Exercise 1 – Create a Flask App

Exercise 2 – Dynamic Route

Exercise 3 – Return JSON