# Databases With FastAPI — Django / FastAPI

Source: https://www.skillbyai.com/en/django-fastapi/p-data

> SQLAlchemy, SQLModel and migrations.

## Bring your own data layer

FastAPI has no built-in ORM. Common choices are **SQLAlchemy 2.x** (sync or async sessions), **SQLModel** (SQLAlchemy plus Pydantic models in one class), or async drivers directly; **Alembic** handles migrations. Provide sessions through a `yield` dependency, keep transactions short, and validate input with Pydantic before it reaches the database. For simple CRUD on a relational model with an admin, Django may be the faster path.

## A session dependency with SQLAlchemy (sketch)

Not run here; check the framework documentation for your version.

```python
from sqlalchemy import create_engine, select
from sqlalchemy.orm import Session

engine = create_engine("postgresql+psycopg://shop@db/shop", pool_pre_ping=True)

def get_session():
    with Session(engine) as session:     # closed automatically after the request
        yield session

@app.get("/products/{pid}")
def read(pid: int, session: Annotated[Session, Depends(get_session)]):
    product = session.get(Product, pid)
    if product is None:
        raise HTTPException(404, "Not found")
    return product
```

## Use Alembic for schema changes

Generate migrations with alembic revision --autogenerate, review them, and apply them in deployment.

**Quiz:** Which tool commonly manages schema migrations for SQLAlchemy?

- [x] Alembic
- [ ] Django admin
- [ ] Pydantic
- [ ] uvicorn

*Answer:* Alembic. Migrations are separate from FastAPI.