如何使用Flask-Migrate拓展数据库表结构

pip3 install flask-migrate
pip3 install flask-script

#coding=utf-8
from flask import Flask

from flask_sqlalchemy import SQLAlchemy
from flask_migrate import Migrate,MigrateCommand
from flask_script import Shell,Manager

app = Flask(__name__)
manager = Manager(app)

app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql://root:mysql@127.0.0.1:3306/Flask_test'
app.config['SQLALCHEMY_COMMIT_ON_TEARDOWN'] = True
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = True
db = SQLAlchemy(app)

#第一个参数是Flask的实例，第二个参数是Sqlalchemy数据库实例
migrate = Migrate(app,db) 

#manager是Flask-Script的实例，这条语句在flask-Script中添加一个db命令
manager.add_command('db',MigrateCommand)

#定义模型Role
class Role(db.Model):
  # 定义表名
  __tablename__ = 'roles'
  # 定义列对象
  id = db.Column(db.Integer, primary_key=True)
  name = db.Column(db.String(64), unique=True)
  user = db.relationship('User', backref='role')

  #repr()方法显示一个可读字符串，
  def __repr__(self):
    return 'Role:'.format(self.name)

#定义用户
class User(db.Model):
  __talbe__ = 'users'
  id = db.Column(db.Integer, primary_key=True)
  username = db.Column(db.String(64), unique=True, index=True)
  #设置外键
  role_id = db.Column(db.Integer, db.ForeignKey('roles.id'))

  def __repr__(self):
    return 'User:'.format(self.username)


if __name__ == '__main__':
  manager.run()

python3 xxx.py db init

python3 xxx.py db migrate -m"版本名(注释)"

python3 xxx.py db upgrade

python 文件 db migrate -m"新版本名(注释)"

python3 xxx.py db upgrade

python xxx.py db history

python xxx.py db downgrade(upgrade) 版本号