Creating tables (db.create_all) in Flask - Try It Yourself

Creating Tables with Flask and SQLAlchemy

📖 Scenario: You are building a simple web app to store information about books in a library. You want to create a database table to hold the book details.

🎯 Goal: Create a Flask app with SQLAlchemy that defines a Book model and creates the corresponding table in the database using db.create_all().

📋 What You'll Learn

Create a Flask app instance named app

Create a SQLAlchemy database instance named db linked to app

Define a Book model with columns id (integer primary key), title (string), and author (string)

Use db.create_all() to create the tables in the database

💡 Why This Matters

🌍 Real World

Creating tables is the first step in building web apps that store data persistently, like user info, products, or posts.

💼 Career

Understanding how to define models and create tables is essential for backend web development roles using Flask and SQLAlchemy.

1

Set up Flask app and SQLAlchemy

Create a Flask app instance called app and configure it with SQLALCHEMY_DATABASE_URI set to 'sqlite:///library.db'. Then create a SQLAlchemy instance called db linked to app.

Flask

# Create Flask app instance named app
# Configure app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///library.db'
# Create SQLAlchemy instance named db linked to app
# Your code here

Need a hint?

Use Flask(__name__) to create the app. Set app.config['SQLALCHEMY_DATABASE_URI'] to the SQLite file path. Then create db = SQLAlchemy(app).

2

Define the Book model

Define a class called Book that inherits from db.Model. Add three columns: id as an integer primary key, title as a string of max length 100, and author as a string of max length 50.

Flask

from flask import Flask
from flask_sqlalchemy import SQLAlchemy

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

# Define Book model with id, title, author columns
# Your code here

Need a hint?

Define a class Book inheriting from db.Model. Use db.Column to define each column with the right type and primary key for id.

3

Create the tables in the database

Call db.create_all() to create the tables in the database based on the models defined.

Flask

from flask import Flask
from flask_sqlalchemy import SQLAlchemy

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

class Book(db.Model):
    id = db.Column(db.Integer, primary_key=true)
    title = db.Column(db.String(100))
    author = db.Column(db.String(50))

# Create all tables in the database
# Your code here

Need a hint?

Use db.create_all() to create tables for all models in the database.

4

Run the Flask app

Add the code to run the Flask app by calling app.run() inside the if __name__ == '__main__': block.

Flask

from flask import Flask
from flask_sqlalchemy import SQLAlchemy

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

class Book(db.Model):
    id = db.Column(db.Integer, primary_key=true)
    title = db.Column(db.String(100))
    author = db.Column(db.String(50))

db.create_all()

# Add code to run the Flask app
# Your code here

Need a hint?

Use the standard Python block if __name__ == '__main__': and call app.run() inside it to start the Flask server.