关系映射字段的值为空

# 示例代码（Python + SQLAlchemy）
from sqlalchemy import Column, Integer, String, ForeignKey
from sqlalchemy.orm import relationship
from sqlalchemy.ext.declarative import declarative_base

Base = declarative_base()

class User(Base):
    __tablename__ = 'users'
    id = Column(Integer, primary_key=True)
    name = Column(String)

class Post(Base):
    __tablename__ = 'posts'
    id = Column(Integer, primary_key=True)
    title = Column(String)
    user_id = Column(Integer, ForeignKey('users.id'))
    user = relationship("User")

# 插入数据时确保user_id被赋值
new_user = User(name="John Doe")
session.add(new_user)
session.commit()

new_post = Post(title="My First Post", user_id=new_user.id)
session.add(new_post)
session.commit()

-- 检查表结构
DESCRIBE posts;

-- 确保user_id允许NULL值或存在对应的user_id
ALTER TABLE posts MODIFY user_id INT NULL;

// 示例代码（Node.js + Sequelize）
const User = require('./models/User');
const Post = require('./models/Post');

async function createPost(title, userId) {
    const newPost = await Post.create({ title, userId });
    return newPost;
}