Using Flask‑SQLAlchemy for Database Operations in Python Web Development

Background: In web development, databases are essential and SQLAlchemy is the most popular ORM for Python; Flask‑SQLAlchemy simplifies its integration with Flask.

Installation: Use pip install flask-sqlalchemy to add the package.

Configuration: Add database URI and other settings in the Flask app, e.g.,

app.config['SQLALCHEMY_DATABASE_URI']='mysql+pymysql://user:pwd@host:port/flask_test?charset=utf8&autocommit=true'

and app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = True, then initialize with db = SQLAlchemy(app). More options are listed at the official config page.

Model definition: Each table corresponds to a class inheriting from db.Model; define columns with Column types and optionally a __repr__ method.

Data retrieval: Query the database directly and render results in HTML templates; pagination can be handled on the front‑end with DataTables or on the back‑end using limit and offset methods.

Updating data: After editing or creating records, commit changes with db.session.commit(). An example shows using an id check to distinguish insert versus update.

Join queries: Flask‑SQLAlchemy supports joins via the join method; an example demonstrates joining three tables to select specific fields:

news = db.session.query(Table1.param1, Table1.params2).join(Table2, Table2.params1==Table1.params1).join(Table3, Table3.params1==Table1.params1).first()

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The tutorial ends with a note that more Flask features will be shared later.