Database migrations with Flask-Migrate - Mini Project: Build & Apply

Database migrations with Flask-Migrate

📖 Scenario: You are building a simple Flask web app to manage a list of books. You want to keep your database structure organized and easy to update as your app grows.

🎯 Goal: Learn how to set up Flask-Migrate to handle database migrations. You will create the initial database model, configure Flask-Migrate, generate a migration script, and apply it to update the database.

📋 What You'll Learn

Create a Flask app with SQLAlchemy and a Book model

Configure Flask-Migrate with the Flask app and database

Generate an initial migration script for the Book model

Apply the migration to create the books table in the database

💡 Why This Matters

🌍 Real World

Database migrations help developers update database structures without losing data. This is essential when apps grow and change.

💼 Career

Knowing Flask-Migrate is important for backend developers working with Flask apps to maintain and evolve databases safely.

1

Create the Flask app and Book model

Create a Flask app instance called app. Set up SQLAlchemy with db = SQLAlchemy(app). Define a Book model with id as an integer primary key and title as a string column.

Flask

# Create Flask app and Book model
# Your code here

Need a hint?

Remember to import Flask and SQLAlchemy. Set the database URI to use SQLite file books.db.

2

Configure Flask-Migrate

Import Migrate from flask_migrate. Create a migrate object with migrate = Migrate(app, db) to link Flask-Migrate with your app and database.

Flask

from flask import Flask
from flask_sqlalchemy import SQLAlchemy

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///books.db'
db = SQLAlchemy(app)

class Book(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    title = db.Column(db.String(100), nullable=False)

# Configure Flask-Migrate here
# Your code here

Need a hint?

Import Migrate and create the migrate object after setting up db.

3

Generate the initial migration script

Use the Flask CLI command flask db init to create the migrations folder. Then run flask db migrate -m "Initial migration" to generate the migration script for the Book model.

Flask

# Run the following commands in your terminal:
# flask db init
# flask db migrate -m "Initial migration"

Need a hint?

These commands are run in the terminal, not in Python code. They create migration files for your database changes.

4

Apply the migration to update the database

Run the Flask CLI command flask db upgrade in your terminal to apply the migration and create the books table in the database.

Flask

# Run the following command in your terminal:
# flask db upgrade

Need a hint?

This command applies the migration changes to your database. Run it in the terminal.