如何使用flask-sqlalchemy查询博客帖子的类别？

pip install Flask
pip install Flask-SQLAlchemy

from flask import Flask
from flask_sqlalchemy import SQLAlchemy

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = '数据库连接URL'
db = SQLAlchemy(app)

class Post(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    title = db.Column(db.String(100))
    content = db.Column(db.Text)
    category_id = db.Column(db.Integer, db.ForeignKey('category.id'))
    category = db.relationship('Category', backref=db.backref('posts', lazy='dynamic'))

class Category(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(50))

flask db init
flask db migrate
flask db upgrade

categories = Category.query.all()
for category in categories:
    print(category.name)