Chapter 2. Relational Databases with SQLAlchemy

Relational databases are the bedrock upon which almost every modern Web application is built. Learning to think about your application in terms of tables and relationships is one of the keys to a clean, well-designed project. As you will see in this chapter, the data model you choose early on will affect almost every facet of the code that follows. We will be using SQLAlchemy, a powerful object relational mapper that allows us to abstract away the complexities of multiple database engines, to work with the database directly from within Python.

In this chapter, we shall:

• Present a brief overview of the benefits of using a relational database
• Introduce SQLAlchemy, the Python SQL Toolkit and Object Relational Mapper
• Configure our Flask application to use SQLAlchemy
• Write a model class to represent blog entries
• Learn how to save and retrieve blog entries from the database
• Perform queries – sorting, filtering, and aggregation
• Build a tagging system for blog entries
• Create schema migrations using Alembic