如何从flask sqlalchemy数据库中删除或修改表

from flask_sqlalchemy import SQLAlchemy

db = SQLAlchemy()

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

# 删除所有表
db.drop_all()

# 或者删除特定表
db.session.remove()
db.engine.execute('DROP TABLE my_table;')

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

class MyTable(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(100))  # 修改字段长度
    new_column = db.Column(db.String(50))  # 添加新字段

flask db migrate -m "modify table"
flask db upgrade