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.
Read MoreFlask and Database Connection: SQLAlchemy Basic Operations
SQLAlchemy is a popular ORM tool for Python that allows database operations through Python classes/objects, avoiding direct SQL writing. It supports multiple databases (e.g., MySQL, SQLite) and is well-suited for Flask development. Installation requires `pip install flask flask-sqlalchemy`, with additional drivers needed for databases like MySQL. During initialization, configure the Flask application and database connection (e.g., SQLite path), then initialize the SQLAlchemy instance. Data models are defined via classes, where each class corresponds to a table and class attributes represent fields (e.g., the `User` class includes `id`, `username`, etc., with primary key, unique, and non-null constraints). Use `db.create_all()` to generate tables within the application context. Core operations (CRUD): Create (instantiate → `db.session.add()` → `commit()`); Read (`query.all()`/`filter_by()` etc.); Update (modify object attributes → `commit()`); Delete (`db.session.delete()` → `commit()`). Workflow: Configure connection → Define models → Create tables → CRUD operations. The advantage is no need to write SQL, facilitating rapid development.
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