How do I delete DB (sqlite3) in Django 1.9 to start from scratch?

rm -f tmp.db db.sqlite3 rm -r my-app/migrations python manage.py makemigrations python manage.py migrate

Removes the database.
Removes the migrations from your app.
Re-runs the migrations. Note: you could also do: python manage.py makemigrations my-app
Migrate changes.

1. Delete the sqlite database file (often db.sqlite3) in your django project folder (or wherever you placed it)
2. Delete everything except __init__.py file from migration folder in all django apps (eg: rm */migrations/0*.py)
3. Make changes in your models (models.py).
4. Run the command python manage.py makemigrations or python3 manage.py makemigrations
5. Then run the command python manage.py migrate.

That's all.

If your changes to the models are not detected by makemigrations command, please check this answer