Creating tables (db.create_all) in Flask - Quick Revision & Summary

Recall & Review

beginner

What does db.create_all() do in Flask-SQLAlchemy?

db.create_all() creates all the tables defined by your models in the connected database. It sets up the database structure based on your Python classes.

beginner

When should you call db.create_all() in a Flask app?

You call db.create_all() after defining your models and before running your app, usually once to set up the database tables.

intermediate

Does db.create_all() update existing tables if the model changes?

No, db.create_all() only creates tables if they don't exist. It does not modify existing tables. For updates, you need migrations.

beginner

What is a simple example of using db.create_all() in a Flask app?

<pre>from flask import Flask
from flask_sqlalchemy import SQLAlchemy

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

class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(80))

with app.app_context():
    db.create_all()</pre>

intermediate

Why do you need app.app_context() when calling db.create_all()?

Flask needs an application context to know which app and database to use. app.app_context() activates this context so db.create_all() works properly.

What does db.create_all() do in Flask-SQLAlchemy?

A Creates all tables defined by models if they don't exist

B Deletes all tables in the database

C Updates existing tables to match models

D Runs database migrations automatically

db.create_all() creates tables only if they don't exist. It does not delete or update tables.

Which of these is required before calling db.create_all()?

A A migration script

B A running web server

C A database backup

D An active Flask application context

You must have an active Flask app context so Flask knows which app and database to use.

If you change a model after calling db.create_all(), what happens when you call it again?

A Tables are updated automatically

B No changes happen to existing tables

C Old tables are deleted and recreated

D An error is thrown

db.create_all() does not update existing tables. You need migrations for that.

Which database URI is used in this example: sqlite:///mydb.sqlite?

A A local SQLite file database

B A remote MySQL server

C An in-memory PostgreSQL database

D A cloud MongoDB database

This URI points to a local SQLite file named mydb.sqlite.

What is the main limitation of db.create_all()?

A It requires manual SQL commands

B It only works with MySQL

C It cannot modify existing tables

D It deletes all data when run

db.create_all() only creates missing tables; it does not alter existing ones.

Explain how db.create_all() works and when you should use it in a Flask app.

Think about setting up your database structure before running your app.

Describe why db.create_all() is not enough to update your database schema after model changes.

Consider what happens when your app grows and models change.