如何将使用SQLAlchemy制作的数据库导入Flask应用程序？

from flask import Flask
from flask_sqlalchemy import SQLAlchemy

app = Flask(__name__)

app.config['SQLALCHEMY_DATABASE_URI'] = '数据库连接信息'

db = SQLAlchemy(app)

class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(80), unique=True, nullable=False)
    email = db.Column(db.String(120), unique=True, nullable=False)

    def __repr__(self):
        return '<User %r>' % self.username

@app.route('/')
def index():
    # 创建数据库记录
    user = User(username='John', email='john@example.com')
    db.session.add(user)
    db.session.commit()

    # 查询数据库记录
    users = User.query.all()

    # 更新数据库记录
    user = User.query.filter_by(username='John').first()
    user.email = 'new_email@example.com'
    db.session.commit()

    # 删除数据库记录
    user = User.query.filter_by(username='John').first()
    db.session.delete(user)
    db.session.commit()

    return 'Hello, World!'