从FastAPI中发布的Pydantic模型更新SQLAlchemy ORM现有模型？

from fastapi import FastAPI
from pydantic import BaseModel
from sqlalchemy import create_engine, Column, Integer, String
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker

app = FastAPI()
SQLALCHEMY_DATABASE_URL = "sqlite:///./test.db"  # 替换为你的数据库连接
engine = create_engine(SQLALCHEMY_DATABASE_URL)
SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
Base = declarative_base()

class ItemBase(BaseModel):
    name: str
    description: str

class ItemCreate(ItemBase):
    pass

class Item(ItemBase):
    id: int

    class Config:
        orm_mode = True

class DBItem(Base):
    __tablename__ = "items"

    id = Column(Integer, primary_key=True, index=True)
    name = Column(String, index=True)
    description = Column(String)

Base.metadata.create_all(bind=engine)

@app.post("/items/", response_model=Item)
def create_item(item: ItemCreate, db: Session = Depends(get_db)):
    db_item = DBItem(**item.dict())
    db.add(db_item)
    db.commit()
    db.refresh(db_item)
    return db_item

@app.put("/items/{item_id}", response_model=Item)
def update_item(item_id: int, item: ItemCreate, db: Session = Depends(get_db)):
    db_item = db.query(DBItem).filter(DBItem.id == item_id).first()
    db_item.name = item.name
    db_item.description = item.description
    db.commit()
    db.refresh(db_item)
    return db_item