flask-sqlalchemy中的自引用数据库查询。社交媒体应用

from flask import Flask
from flask_sqlalchemy import SQLAlchemy

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'your_database_uri'
db = SQLAlchemy(app)

class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(50))
    followers = db.relationship('User', secondary='followers',
                                primaryjoin=('followers.c.follower_id == User.id'),
                                secondaryjoin=('followers.c.followed_id == User.id'),
                                backref=db.backref('followed_by', lazy='dynamic'),
                                lazy='dynamic')

followers = db.Table('followers',
                     db.Column('follower_id', db.Integer, db.ForeignKey('user.id')),
                     db.Column('followed_id', db.Integer, db.ForeignKey('user.id'))
                     )

# 查询某个用户的粉丝列表
user = User.query.filter_by(name='username').first()
followers = user.followers.all()

# 查询某个用户关注的用户列表
user = User.query.filter_by(name='username').first()
followed_users = user.followed_by.all()