Your database connection is configured via:

• SQLALCHEMY_DATABASE_URISQLALCHEMY_DATABASE_URI

SQLite (easy for learning)

app.config["SQLALCHEMY_DATABASE_URI"] = "sqlite:///app.db"

app.config["SQLALCHEMY_DATABASE_URI"] = "sqlite:///app.db"

Meaning:

• store the database file app.dbapp.db in your project directory

Postgres (common in production)

A typical URI format:

• postgresql://username:password@host:port/database_namepostgresql://username:password@host:port/database_name

Example:

app.config["SQLALCHEMY_DATABASE_URI"] = "postgresql://myuser:mypassword@localhost:5432/mydb"

app.config["SQLALCHEMY_DATABASE_URI"] = "postgresql://myuser:mypassword@localhost:5432/mydb"

Security best practice

Never hardcode passwords in code.

Use environment variables:

import os
app.config["SQLALCHEMY_DATABASE_URI"] = os.environ.get("DATABASE_URL")

import os
app.config["SQLALCHEMY_DATABASE_URI"] = os.environ.get("DATABASE_URL")

A note about DATABASE_URL formats

Some platforms provide DATABASE_URLDATABASE_URL like:

• postgres://...postgres://...

SQLAlchemy expects postgresql://...postgresql://....

You may need to normalize it depending on your deployment platform.