Flask and Database: SQLAlchemy Model Definition

This article introduces the method of database interaction in Flask using SQLAlchemy (an ORM tool). The core steps are as follows: First, install Flask and Flask-SQLAlchemy. For development environment with SQLite, no additional driver is needed; other databases require corresponding drivers (e.g., pymysql for MySQL). Next, initialize the Flask application and SQLAlchemy, configure the SQLite database connection (URI: sqlite:///mydatabase.db), and disable modification tracking to reduce overhead. Then, define models: Use Python classes inheriting from db.Model to map database tables. Class attributes correspond to fields (e.g., id as primary key, username as non-null unique string), supporting various field types (Integer, String, Text, etc.). Table relationships are defined using foreign keys and relationships (e.g., one-to-many relationship between User and Article). Create tables by executing db.create_all() within the application context, which automatically generates the table structure. Finally, perform CRUD operations via db.session: Add using add + commit, query using query.all/filter_by, update by directly modifying attributes then commit, and delete using delete + commit. Summary: Model definition is the foundation of Flask database interaction. Data operations can be implemented by mapping fields and relationships through class attributes, with table relationships extensible for future use.