Database migrations with Flask-Migrate - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

What is the primary purpose of Flask-Migrate?

Flask-Migrate is a tool used in Flask applications. What does it mainly help developers do?

A Automatically generate HTML forms for database models

B Manage database schema changes over time using migrations

C Handle user authentication and authorization

D Serve static files like images and CSS

💡 Hint

Think about how your database structure changes as your app grows.

Flask-Migrate helps developers apply and track changes to the database schema safely using migration scripts.

❓ component_behavior

intermediate

What happens when you run 'flask db migrate'?

In a Flask app using Flask-Migrate, what does the command 'flask db migrate' do?

A Creates a new migration script by comparing models to the current database schema

B Applies all pending migrations to the database

C Deletes all migration scripts

D Rolls back the last applied migration

💡 Hint

This command prepares changes but does not apply them yet.

'flask db migrate' generates a migration script reflecting model changes but does not update the database.

📝 Syntax

advanced

Identify the correct way to initialize Flask-Migrate

Given a Flask app and SQLAlchemy db instance, which code correctly initializes Flask-Migrate?

Flask

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from flask_migrate import Migrate

app = Flask(__name__)
db = SQLAlchemy(app)

# Which line correctly initializes Migrate?

A migrate = Migrate(app, db)

B migrate = Migrate(db, app)

C migrate = Migrate(app)

D migrate = Migrate(db)

💡 Hint

Check the order of arguments in the Migrate constructor.

Flask-Migrate requires the Flask app first, then the database instance to initialize properly.

❓ state_output

advanced

What is the state of the database after 'flask db upgrade'?

After running 'flask db upgrade' in a Flask app using Flask-Migrate, what is true about the database?

A The database schema is rolled back to the previous migration

B The database schema is reset to the initial empty state

C No changes are applied to the database schema

D The database schema matches the latest migration scripts

💡 Hint

This command applies all migrations that have not been applied yet.

'flask db upgrade' applies all pending migrations so the database schema is up to date.

🔧 Debug

expert

Why does 'flask db migrate' fail with 'Target database is not up to date'?

You run 'flask db migrate' but get an error: 'Target database is not up to date'. What is the most likely cause?

A The Flask app is missing the SQLAlchemy db instance

B The migration folder is missing

C There are unapplied migrations; you must run 'flask db upgrade' first

D The database URI is incorrect in the Flask config

💡 Hint

Think about the order of applying migrations before creating new ones.

Flask-Migrate requires the database to be at the latest migration before creating new migration scripts.